I chased a parasitic draw on my 2010 Ram for months. I even took it to a dealer and a local shop after I failed to find the culprit. They couldn't pinpoint it either. I checked everything...or so I thought. Just by dumb luck, I dropped something in the driveway at night and it rolled under my truck. I glanced up and saw a faint light in the engine bay. Turns out that the hood latch (and the hood light actuator/switch) was slightly askew. The hood would latch, but since the latch was out of position, the light switch never disengaged. Makes sense that this light would never show a draw as I would disconnect the hood light at the bulb connector since I had the hood open testing for current draw. Crazy stuff, but I learned a lot from videos like this one. Hopefully, my story helps someone out. Thanks!
Good share. I have a Lexus gx470 and still has current draw. I did the Eric the car guy method and put the meter in series with the negative cable and pulled all the fuses and nothing changed. So I’m a bit lost. I’ll try humble mechanics method soon
@@stallion78 if you have a draw with all the fuses pulled then I would next disconnect your starter main Cable and alternator main cable. I’ve had both of those cause draws on higher mileage cars. They corrode internally causing a faint connection to ground. Also people forget that a dirty battery case can cause a very small draw. Voltage can travel all the way across a battery top from post to post. It’s rare but is possible
H! my brother-in-law just prior to shipping out to Viet Nam placed a light in his trunk so you could see at night while in the truck Turns out the light was not going off after my sister replaced the battery commandeered her father, my dad who failed to find it. I think they accidently found it somewhat like you did. WHO KNEW? LOL
I did something similar decades ago on a car that kept killing batteries. Turns out the glove box plunger was askew and the glovebox light was on even with the door closed. Took hours to find it even though I knew it was a light issue (couldn't see the light in broad daylight)
I've been a master tech DIYer , weekend warrior, shade tree mechanic , jack of all trades master of none, under sensai mr Miyagi, for the past 30 years never ever seen such a great great video'. Thanks!
I've been a master tech for 25 years and never once did I think about physically latching the doors etc. And this is a great method for finding gremlins. I'm glad I found this channel, as unusual even as good as I am in still learning! Awesome video
Yeah ok, and then there's most vehicles whose switches are NOT in the latch. Furthermore if you've got a drop across the fuse, there's a problem with that fuse. Sleeping vehicles should not be drawing unless you've got a module that's not going to sleep either because it's bad or somebody wired in (added) something wrong which is what I see all too frequently. ua-cam.com/video/6xFo_oHFF48/v-deo.html
@@rjbradlow pretty sure I didn't need the lecture. And testing for voltage drop is easy. I'm not sure what you've been working on but pretty much everything made in the last ten years has the switch in the latch. Wondering why you're replying this way to my comment, seems to me you either have a problem with the video, which I didn't make, or me personally which makes you a bit of a child
I've been a tech for over 25 years. I thought I was pretty good at electrical diagnostics. This video set me straight. What a great technique. Thanks for these videos. I wish these were around in the 90's.
@@HumbleMechanic About to buy an 06 without radio. Owner says radio is killing battery. Great video! Does replacing with aftermarket radio fix the battery drain issue?
I am a 12v technician at a car audio shop. The number of dealership techs that don't know how to do a proper current draw test is mind boggling. I get a couple cars a month that are misdiagnosed because of poor electrical troubleshooting. If every tech watched this video the world would be a better place. And if you do this for a living Blue Point has a tool called the Amp Hound which does the fuse type current drop for you so it speeds up the job and makes you more efficient.
I’ve used this method with success several times. I’ve recently learned an extra hint to go along with this test. Prior to testing each fuse(especially with vehicles with a large amount of fuses), use a thermal image camera to look at the fuses. The one with the draw will show up warmer than the rest. Helps pinpoint the circuit quickly.
Valid tip but most don't have one. However, many have an infrared temp gun. Not as quick and easy but it too can point you in the right direction quicker.
Some of the new fuses now don’t have the test spots on the back because engineers decided that was too handy and they pride themselves in making things more difficult for us mechanics. Great video man
their ideal aim is to make things impossible for mechanics & diyrs, but the right to work attorneys need to pass a law that requires all favtories & dealers doing this to admit before sale, that the buyer now has no choice but to go to the corrupt, triple priced dealers every time- the headline of this warning should be, WARNING: we now own your S. 👋😒
I have seen test points extremely corroded esp living near beaches, I wonder if sealed fuses just make better sense. Only seen a couple, but some have corroded into fuse plastic. Never caused me issues but something to wonder about for small fuses especially
Had a draw on a skid steer. Not as much out there for help with equipment as there is for automotive. A fuse panel is a fuse panel so I administered your test and used in line amp draw method. Ended up being a bad starter. Thank you for taking the time to share the knowledge
Stewart W - was the starter drawing current when it was just sitting unused ? I know the old cars voltage regulators would do that at times. Was it a bad solenoid \ relay staying partly closed drawing current?
Best parasitic draw video out there. One note: good test leads are not cheap. If your multimeter does not read zero ohms, Fluke says that is just increasing resistance as the meter electrical contacts, and the lead connections get dirty or corroded over time. If cleaning with contact cleaner, or isopropyl alcohol doesn't work, you can use the "relative" button on the meter to adjust for the increasing resistance. Set to ohms, touch the leads together, push the "relative/rel" button, and the display will read zero. Fluke says you only need to throw the leads away when the wires become exposed, or broken.
This guy is easy to watch and always adds little touches of experience that simply following an instruction manual doesn't give you. Always good to see a Humble Mechanic video appear in my Google search results...
When I worked as a diesel mechanic it was always aftermarket shit. Even high end GPS trackers that were tamperproof. Always start with aftermarket add ons.
I feel we are blessed to have you and several others on UA-cam sharing your knowledge with us . Those who do not wish to learn and those jealous of your knowledge and capabilities will always try to discourage others . I am 51 and wish training videos like yours were available when I was in my teens . Truly truly helpful . Thanks for all your work .
Electrical Engineer here; didnt realize that fuses has a large enough resistance to them to detect a significant enough voltage drop to calc amperage off of. Interesting technique. Thanks.
They're meant to melt at certain current. So it would have to be resistive to cause heat, thus generating voltage across it prior to meltdown. Even copper traces on PCB's have significant enough voltage drops, thus we utilize Kelvin connections. 😉
One small correction to note. 1006 in speaking of amps is 1.006A not .1A, simple mistake but for students it could be detrimental when they are struggling to understand 1000mV is 1V ect. Good video, glad to see other putting things out like this to help promote the industry.
@Get on the cross and don’t look back You are using the wrong scripture for your audience. These people are dealing with electrical issues. Try, John 8:12 “Then Jesus spoke again to them, saying: “I am the light of the world. Whoever follows me will by no means walk in darkness, but will possess the light of life.’
Great video and information. I personally disconnected the battery + and put my amp meter between the plus and the plus cable (10 A setting). I looked the doors and after the car went to sleep I saw a parasite draw of 250 mA. I reconnected the battery locked the doors and checked every single fuse like you did in the video. No draw found. I disconnected the battery again and hooked everything up like before. Then I disconnected the alternator lead from the alternator and the draw was 25mA. So my parasite draw was from the alternator. Since the alternator in my car is not fused I wouldn't be able to find the fault with your method alone
For new viewers, just an observation that 1006 milliamps is just over 1 amp, not 0.1 amp as was said at 7:06. Humble Mechanic has acknowledged that he mis spoke in old comments below.
@@realSamAndrew But the mentioned discrepancy was .006, The remainder of the equations faulty fraction representation. And if this is the only fault in the presentation, of which the methodology is not just out of box, it ate it, Dude is batting 999.9? Divergent thinking is the undercurrent of innovation topping it off with someone who will actually show it to anyone/everyone? RARE!. This is better in so many ways and probably some I am not seeing . Props to ya and thank you HumbleMechanic
Ludicrous speed, I agree with you but you missed the point of my comment. I am not even concerned with the roundup which didn't strike me as an error. It was a typo which turned out to change the scale. It made a fairly insignificant amount into a huge serious amount. It also would lead the viewer to think that he was doing it wrong if he got a different answer. The rest of your comment is spot on the method is fantastic and the presentation was fantastic. Accuracy was the only small item and by correcting it it makes the video much better not worse. I am grateful for all sincere helpful comments and mine was meant to be that as well . I Thank the other commenters for pointing this out and also everyone who adds other helpful information
@@realSamAndrew I didn't even see it that way. It felt like just another comment section "stab you in the back to boost my ego" if you follow. I see it so much in videos where the maker is helping everyone and people say the most asinine shit and sometimes I feel compelled to say something only because it seems like the right thing. WOW the world would be so much better if we could all chill the hell out and simply be civil with each other,most of the crap is just misunderstanding anyway. THIS TIME I'm glad it was my mistake! Unfortunately most of the time I'm not mistaken. Nice bumping into you!
Its very important to check fuses before start metering. If a fuse is blown you might have 12v on one side and ground on the other (through a windshieldmotor or windowheater etc) and your multimeter might get damaged when measuring up to 300mV. Set meter to 20v dc atleast and do this test before switching over to 300mV.
Qualified automotive electrician for 15 years and have never seen this method before! Seems way superior! Never too old to learn something new 🤙 cheers!
Ran into problems trying to do parasitic draw test after watching videos where they pull the fuses. Aside from forums (TDI Club, VW Vortex), this has been the most straightforward explanation on how to see if anything is draining my battery. Thank you!!
Car newbie here. I was super excited to try what you talked about. I had to do several adjustments and it took me quite awhile to understand everything, but I found out I had such a huge draw by my burglar alarm I had to adjust my meter up to volts from millivolts to get reading. I sure hope you have a video about this now. Thanks, a very informative video.
As a vw master technician myself, this has always been useful. I now work for audi, been there 3 weeks and taught my shop foreman how to do it this way...he was so confused at first lol then he made sense of what we were looking at. He found this easier.
@@vduber03 It might still be useful. ...If Jose had a 'dead short', then he'd know the faulty circuit by the fuse blown , however , if it's a partial short , then it can be a low current leakage and isolated as shown in the vid. If he does have a dead short then replacing the fuse with a mini circuit breaker breaker helps in the diagnosis procedure .
Oh my lord! Great Video! Didn't even think about 'putting the car to sleep', Thanks Charles! My wife's 2007 Toyota Corolla is suddenly draining the battery if not driven every day or two. Replaced the battery, did the 'disconnect the battery cable' parasitic draw test and found only about a 30mA draw. Charging system 13.4-14.2VDC, no idiot lights, however I believe it's the OEM alternator (only about 78K miles)...so still not ruling the alternator or regulator out. But never thought about latching the doors and putting it to sleep...outstanding advice.
I have a 2004 Chrysler Crossfire. Over the last few years two seemingly unrelated things started to happen. The first was that when driving on hot days - say more than 33 DegC [91.5 DegF] - the Security Alarm would start and would eventually stop after lifting the bonnet (to cool things under there down). The second was that the virtually new heavy duty battery would not hold its charge more than about a month or so. I finally decided to address them with the battery-drain being the first; and, following this video’s instructions to the letter, found that all fuses gave less than 0.1 mV EXCEPT the one which combined the interior roof light, the boot light and the Anti-Theft Alarm Unit, which gave a reading of 0.6 mV. Upon disconnecting the Alarm Unit the reading on the fuse (No 9 in my car) dropped to 0.1 mV. Obviously the Alarm Unit has a fault, which I’m going to follow-up. So, THANK YOU VERY MUCH “The Humble Mechanic” for your really useful method of finding battery drain problems. In my case it’s solved 2 problems at once!! 😊😊
great idea and great way to do a parasitic draw test. However, i will suggest(after doing all preliminary work you did with latching doors and hood) use of a clamp-on probe on negative side of battery with arrow facing away from battery and if you read any Amps then you have a parasitic draw. then you do same in positive cables and when find which positive cable has the draw then trace it. if it goes to front distribution box then you do voltage drops on fuses as you did and go with the chart(great tool by the way). if positive cable goes to rear distribution you do voltage drop there and no need to waste time doing front or side or whenever the distribution can be. Modern cars have 5-6-7 or 8 boxes with fuses so will be a great idea to focuse on the power wires that supplies those boxes. when you find the draw on the fuse through volt.drop then you need a wiring diagram to see what that fuse powers because can be 3-4-5 different components. after you find diagram start unplugging one by one the components and when you do so on the bad one you hit the lottery and and your fuse will change reading to 0V.
Good post. In the electrical world we called it divide and conquer. Keep breaking the entire system down to isolate the area. Then once in the right area ( fuse box #XX) do individual testing until you find the draw. Then Bobs your uncle.
I learned a few things for sure. I always test my leads before checking continuity, or ohms. Didn’t think about checking them EVERY time. Solid advise though. Sometimes it’s the little things that will drive you mad. Just had a bad battery on my F100 that passed a charge and load test because it was literally the first thing I checked when my truck wouldn’t start. I knew I had a dead short somewhere. No off gassing, no swelling, no amp draw on the terminals, or fuse box. Truck would not start with a jump. Tested ground cable, solenoid, starter, positive cable, starter cable. Replaced parts that looked sketchy, serviced others. Took a few Saturday afternoons to find before the battery finally stopped taking a charge. Put a new battery on and all problems went with it. Apparently it was only shorting bad enough when I went to discharge it by starting. Otherwise it was powering everything else and showing 12+ volts after a charge....until it didn’t. Let it sit for 3 days to verify that draw was gone.
I had a bad battery connection that allowed all electrical components in the car to work but not start or start poorly. Once the connection was fixed, no problems. I wasn't suspecting a loose battery connection since headlights, etc. were fine.
Thank you so much for this video. My daughter's '06 Beetle convertible developed a parasitic power drain over the past month or so. Following your procedure I narrowed the power draw down to fuse 38. Driver and/or Passenger Door Control Unit. After sitting for 2 hours, fuse 38 was pulling about .8 amps. We had an issue with the driver side door about two months ago where the window wouldn't drop sometimes when opening, and then it wouldn't go back up. Dealership diagnosed it has being out of adjustment. It has been performing normally since then. Before locking the door mechanisms for the diagnostic procedure, I decided to remove the driver side door panel so I could have access to the window motor connector. After two hours of waiting, I verified there was still an approximate .8 amp draw from fuse 38. I unplugged the window motor and the draw went to 0. I plugged it back in and it went back to .8 amps. I may be mistaken, but I think I smelled a slight burnt smell from the window motor control unit when I unplugged it. I think this is the culprit. I am going to order a new motor tomorrow morning and see if this sorts it out. Thanks again!
did it work out ? 800mA is a high draw, and sometimes the plugs on those regulators suffer from high current melting them a bit, so you can see where it's burnt and the plug may need replacing too.
@@DeepakKumar-lv4te yes, we replaced the window motor which has the control module built into it. The current draw stopped, and no more issues with battery drain.
Best video I have seen on this. Working on a kia that we just cant figure out. Changed starter, alternator, battery, power steering and pulleys. Still having draw and cold weather starting. Thanks for the resource.
I wish I had seen this before I went through our bucket truck and started replacing parts...After spending over $2,000 on parts, I finally did this test and found out that our power inverter was the problem. A $2 external power switch, and problem fixed. Thanks for this video! My fault for not googling this before hand lol
Thank you so much for this. I have been trying to figure out how to do a parasitic draw on my homebuilt aircraft and none of the aviation sites were any help. I've been looking for exactly this info for weeks. Seems so easy once someone explains it to you. I appreciate you taking the time to post this.
Learned something new today. Used voltage drops many times before for troubleshooting but never thought of using it to find a parasitic draw. Great video!
Not a techie myself....but I learned 2 things , er maybe 3. How to check the fuses with the probes , how to check my ohms reading on my voltmeter. And to hold on to my 2005 Highlander because it's not as high maintenance as the car you were checking...lol...P.S. ...great presentation . You stayed on point in a highly technical subject . You didn't waste time with lengthy introductions . The length of the video was about the optimal time I want to watch. Others spend 20+ minutes and don't deliver as clear and concise info. Great job.
Thank you. This is the first video (that I have seen) that is accurate and considerate of late model diagnosis. Thank you for stressing the importance of leaving the fuses in place. You briefly mention the interconnectivity of data buses and how one module can wake up another module. You should expand on this in another video. Maybe talk about a draw that is caused by bus activity. A basic video on isolating busses. Sometimes ALL the fuses have high current because nobody goes to sleep. Maybe too complicated for people that aren't techs, but so important for young techs. Again thank you
Thanks for this quick tip, particularly about verifying your probes before beginning to test circuits. That alone is worth the price of admission. As DmcHartsoe pointed out, you might want to say something in your notes, or add something in the video, about the math issues relating to the proper identification of tenths, hundredths and thousandths of a volt in measuring the typically very small voltage drop across an active fuse.
great video , just remember to always make sure your diagnostic scanner is not plugged in and also make sure that key fob is far from the car as this can make some car systems to stay awake.
Hey, before you do any of this. Sit in your car and lock it, keep your ears open and listen for anything or keep your eys out for anything. I heard a thump consistently coming from my driver seat. Turns out my ice scraper was pushing my electric seat back and it couldn't go back any further. But this is the same for something like a stuck hvac actuator clicking or your info screen not turning of cause a fault in your ignition switch. Sometimes it will help you find what fuse to pull durring this test
Wow, I been in the trade for over 40 years, I have a lot of experience with auto electrical and diagnostics and I still learned something today. Thanks for taking the time to make this video. I must admit I generally click on these videos to pick holes in them and occasionally post comments on what they are doing wrong if it is extreme and obvious. :-) Nothing to pick on here (apart from a wee math error :-))
Wow, a UA-cam professor that acknowledges his motives. Never understood what the draw is of basically acting like the know it all each family has that we avoid like the plague and talk shit about whenever his name comes up.
probably because no one does this , im not a mechanic but i am electrician and long time driver , never saw it . If i had to do it , i would check across the battery
I have Citroen c4 grand Picasso 1.6hdi semi automatic after shift could not get reverse but managed to drive home I notice while driving service light keeps flashing what could be thaEexact fault
I've seen this method before, I've actually printed off the charts from power probe myself. Had a company training trip to Lincoln tech in colorado, the lead electronics instructor taught us this method.
If you do this method to the main battery fuses you can also pin point which fuse box is the problem. Each big fuse goes to a fuse box so you can eliminate probably 80% of the potential problems by measuring 5 or 6 fuses.
Great info. One thing to keep in mind if you are looking at older cars, at least through the 1980's with American cars, the dome light switch is in the door jamb by the hinge so closing the latches wouldn't make a difference. Then again, those old cars you could just pull a bulb or two and be done with it.
Some cars has the door jamb switch as well as the latch switch. These circuits are more complex due to alarm systems and to tell the computer that the latch is activated.
Great video - even as an electrical engineer I didn't know the fuse voltage trick! But a slight misstatement regarding your first chart reading - you had a current draw of about 1 amp, not .1 amps as you said.
Great job. Some things I didn't know. I remember we used a test light, before the meters. I miss those days. I was the third generation working in a auto electric shop. we started in 1936. And sadly ended in 2006.
Me “car” is the new house batteries in a C-class RV that would alarm low voltage when used overnight after a full day of driving / charging. This will be a great help! 👍🏻
Found your channel through engineering explained and couldn't be happier I did. I love learning as much as possible about cars since I do all of my own maintenance as well as repairs when I feel confident enough in doing so. Looking forward to watching as many of your videos as I can thanks for what you do for us.
Electronics tech here...might mention that it does take a pretty decent meter to get anything like a semi-accurate reading when getting down into the low mV range. If you are considering trucking over to Hazard Fraught to shell out a whole $10 on a meter, you will certainly get what you pay for. IMO, everyone ought to have a decent meter that they can trust, so maybe a used Fluke on eBay or a Owon or Triplett from Parts Express. Stay away from the $10 stuff.
Jr McDonald - While I totally agree on the quality of the equipment/tools. The fact is that in real life car workshop environment a top of the line ($$$) is a pure waste of money. You want something cheap and simple, that someone will trow a wrench on top and you don't get an hearth attack to see the dollars flying out of the window. Don't ask. LOL :-) With this said the need for very high accuracy in most car testings are not even close to a electronics repair lab counterpart. Some 98% of the work is just like in this video. It's more important to keep the lead tips clean and tested. So, not the $10 for sure, but the $20 should be just fine. ;-)
Jr McDonald ever open one of them 10 dollar suckers up to see what Fry's them? Pretty scary shit. I wouldnt use them on High voltage. Might be your last test. But they make a good door stop in a pinch.
Thanks for this method much better than the pull fuses method (which works) that takes soooo much longer as you have to wait for the car to go back to sleep upon reinserting the fuse. Absolutely brilliant.
My silverado has a screwball terminal style where it screws into the battery. I had no idea how to do a proper draw test with those, but you gave me a solution. Kudos to you, my good sir 👏
Great video! Basically you are measuring the the voltage drop across the fuse just like measuring across a resistor in a circuit. To take it further, if you don't have that handy chart with you, you can always remove the fuse, switch to ohms on meter and use ohms law (V=I*R) to figure out the current draw. It might be a little more accurate as you have real numbers to calculate. Use the battery voltage and divide by resistance. This will give you current in amps. I personally have not used this method but I see that it would be far more superior than other methods. Math never lies. :) Now I am tempted to go to the car and document every fuse draw and save to a list. So if there should be a problem in the future, I know what circuit values should be. Thanks again.
I tell you what a light with two leads can be really handy finding a short to ground. Hook one side to battery +. Then start by pulling out a fuse. Connect the other lead to the + side of where the fuse plugs in. Do that with each circuit. If the light comes on you have a short to ground in that circuit between the battery and the fuse. When the light goes off the short is fixed or just not shorted out. You can use the light and jiggle stuff, close doors, etc to see what causes a temporary short. I did this to isolate a short in the passenger side back door. A yellow wire to the window regulator had missing insulation and would short against the door sometimes when it was closed.
Best explanation on this subject I've seen! Especially like the attention to detail, and memory precautions on taping over the doors in locked positions so you remember NOT to close them during the test. Excellent, sir, excellent. It is noticed.
I do that on a hatch lid to allow the lights to shut off when using the back accessory outlet for charging, but I don't trust myself to notice tape so I put a small block of foam across the latch to keep the bonehead from closing it onto the striker.😜
This gentleman is excellent, voltage drops rule , sometimes calls I R drops , because E= I x R , which is Ohms law , which all you have to know to control electricity learn it love it , I love a large current draw , the sound , the heat , the sparks
Used this method before with no luck.I found the car security system picking up movement,and triggering the alarm System,As we know Modern Security systems are not easily disconnected,they also have internal batteries.
Wow! What a great find this Humble Mechanic is. I'm a fairly good mechanic from years of fixing my own cars, but always learn something new and very useful on this channel. Great explanations, no wasted time! Thank you!
This video was extremely helpful. The guys at the auto shop couldn’t troubleshoot the problem and I had 3 weeks to wait to get it in to the dealer, so I did this test myself and found a failed rear wiper drawing current. Thanks for the help!
this is a great way to check parasitic draws on vehicles and is also great to find dirty connections that can drive you nuts , such as a bad ground problems . same test just a different way to look at it such as from your ground on your battery to any other grounding point that might have a problem
7:05 Where did the 35mA spec come from that he speaks of? Also, aren't there some things that are supposed to be drawing current at all times like the receiver that listens for or detects you key fob, etc.?
New scenario, but happened to me. My body control module was getting wet. Sometimes the AC would not shut off when the car shut off, or the sunroof switches would not work, or other window switches, or.. even the interior lights would not shut off 100% when the doors were closed and the vehicle was locked and alarm system on. My mechanic said it was each system failing, but my carpet being wet told me otherwise. I was shown how the water might have been coming into the car, so I resealed with silicone. FIXED! No more wet carpet or funky electrical draws.
Chart not accessible with link anymore.... Came to this video with doubt and ready to blast you in the comments but left with a little more wisdom. Thanks for this great information! I do electrical work on hotrods and this will be my GO TO method from now on!
Thanks for the video! I've been chasing a parasitic draw down for awhile now and this video made it easy to locate! Thanks again man, you're a life saver
These are great methods! Will try it tomorrow. My Mercedes has two batteries and I havent found an instruction how to troubleshoot that, but your method does not rely on battery disconnection. Great!
I've been doing this without the charts, then going for the circuit with the biggest drop. Thanks for the charts! At first glance I wondered if they actually measured these values, or whether they used Ohm's law, calculating the numbers. A quick back-of-the-envelope check on a couple of chart numbers shows variable resistance depending on amperage, although strangely resistance was lower at higher current for a few. The numbers are really small, so slight corrosion at the tip of the probe might change values. I like your idea to trick the computer into thinking the doors are shut so it will go to sleep.
I would expect a lower voltage drop on a higher amp fuse, after all it does have to carry more current requiring a larger internal fuse element. bigger element carries more currrent without overheating, ie blowing out.
It's not that strange to find lower resistance for the higher rated fuses. Fuse is meant to blow at certain heat developed by current flowing across a resistance. Heat is generated by power dissapation in the resistive material. Power is the current squared x the resistance. Simplistically speaking, if you had same resistance for the higher rated fuse, say 30A, that fuse will blow just the same as the 1A fuse. Of course, they can use different materials to change characteristics of when the material melts with different resistance/current combo.
I'm not going to lie. Most of the cars I've seen with a draw are being sucked down by improperly installed gizmos like big sound systems or aftermarket remote starts. You would not believe the rats nest fluster clucks some people leave under their dash.
Travis Callahan Just a note on batteries: unless you are using the car daily, you're going to have charge loss that takes its toll on battery life. Sitting at partial charge will allow sulfation to develop, and the the battery will hold less and less charge; a catastrophic scenario. It seems nit-picky, but it is true. A good battery maintainer is a smart move. A battery in a car without electrical power-assisted accessories will last quit a bit longer than a car with all the powered accessories.
Lou Fazio - I held onto two extra car batteries for four years by keeping them each on their own maintainer and they still worked great when I finally used them in my car. kind of morbid but I tell people a car battery is like a person the longer they're dead though less chance you have of bringing them back to life. sulfation is a huge killer
not sure what that has to do with my insight but yes batteries discharge over time. but it takes a really long time, unlike a draw that can sometimes drain your charge in a few hours.
Travis Callahan If you're talking to me, I'm saying that battery self-discharge of more than 1 day will begin enough under-charge; adding parasitic load is additional (intentional parasitic and not unintentional shorting). Concerning rat's nest wiring and typical installations, ground loops are beginning to be a consideration for more delicate electronic's connections near larger amperage flows e.g. steering wheel control add-ons for after-market stereos.
civicturbo2009 I'm a big believer in this now. It's just that my previous maintainers always seemed to die out. I'm trying the resonance desulfation (BatteryMinder) now.
A clamp on DC amp meter can't be beat for ease and quickness for finding where a parisitic draw is happening. It takes a little understanding to figure out how to zero out stray magnetic influences that affect the readings but it's worth learning how. A chinesium clamp-on DC amp meter sells for less than 40 bucks on Amazon and every auto mechanic should learn how to use one. They can save a LOT of time!
I have a "couple steps better than cheap" clamp on that comes in very handy, though I'll be replacing it ASAP with a good Fluke unit to augment my 87V.
Wow ,good advice for the volt meter and the leads. Your special Charles and I appreciate the gift of having you. Pesce, respect, blessings in abundance to u and your always my VW car go to guy . Humble indeed
Oh wow, the suspense in automotive diagnostics. The dealership, the manufacturer, nobody knows... As soon as you find the problem that everyone is having, it's gonna be a different diagnosis on the next with the same code......
Thank you, this video was really helpful. (Took me a while to realise I needed to press the open door button on the remote to get those door latches open again though!). I have found the parasitic draw now, it's on a fuse for the ABS and Parking Brake control module. Now what....how do I proceed? Have you got a video for the next step!
Great video. Been wrenching for 35 years and never used this method. I know it works though. I use a tool called Amp Hound. It calculates the the draw for you.
@@Nick-fy7yi I'm old school. Did battery draw with a test light between negative cable and ground, then pull fused till light goes out. This method doesn't work with new cars. Amp draw on each fuse is more precise. There is a tool we use at work called an Amp Hound that does the calculations for you. It works great.
@@tomcisneros5965 yeah I’m in Canada looking for a amp hound can’t find it . My battery is having a parasitic draw and I can’t diagnose where it’s from. Never used a meter of anything before. Brand new battery.
@@Nick-fy7yi I don't remember who makes it , but if you Google Amp Hound it should come up somewhere. In the States you can find it. I don't know how it is there. Try your local part stores as well. You may even find a tool close to it if you ask your parts guy. It's very user friendly.
My thoughts exactly, I now watch this man and scott kilmer. This man explains how and why things happen .Scott gives more of a comedy but both of these gentleman know what they are doing .Fixed couple cars by looking and watching these gentleman
I saw this video and I did subscribe. I’ve just bought the Wife a mint, very low mileage 4.7 Grand Cherokee for Christmas that four days into ownership has a flat battery. I’ve got a new quality battery for it, but I want to find out for sure if it was the old battery that was at fault, (likely, as it won’t fully charge), or it has a parasitic current draw that’s going to leave us with another flat battery.
Very useful info. I have a 2007 Silverado HD2500 crew cab that goes down after a while. It's got two new batteries so there's some parasitic draw happening. This might help figure it out. Thanks.
I have an older Chevy 2500hd 2003 with what's weird is when I bought the truck from my son he didn't mount any trailer brake controller, already in there. But, wires for controller ran from engine compartment to cab through the drivers door above the top hinge. I though this was a rather crude way of running wires from one area to another. But who am I? After a couple months of sitting many times a flat battery would result, and also, this truck has nothing electronic other than aftermarket radio. Crank windows, manual seat. My close friend uses battery tenders for all his battery powered equipment, unfortunately that would hind a problem, like my 2002 honda Forman rubicon 500 for instance, I keep that on tender all year, especially in winter when I need it to be reliable for snow plowing. The honda has a tendency to have a hard time winter starting with much cranking, hence, battery tender. I did change the way I start it though, I choke and push throttle few times, and then turn over with no throttle for 5 seconds trying to create vacuum. Then resume cranking with just plain choke no throttle, fires up. . After charging I will try this, thank you.
Okay, so now it seems so extremely clear how to "close the doors" without actually closing the doors. My EOS has (2) 6V batteries in the trunk. To close the doors, she sat in the back seat to read the MM with leads through the armrest opening. The lead's probe came off of the terminal and for about 5 minutes, we had NO IDEA how I was going to get her out! Then it came back on, so I guess it had temporarily lost contact but came back (it was taped to the top). So dumb, but never again. Thanks for including the latching of the doors, trunk and hood in your video for the infrequent DIYers out here.
I chased a parasitic draw on my 2010 Ram for months. I even took it to a dealer and a local shop after I failed to find the culprit. They couldn't pinpoint it either. I checked everything...or so I thought. Just by dumb luck, I dropped something in the driveway at night and it rolled under my truck. I glanced up and saw a faint light in the engine bay.
Turns out that the hood latch (and the hood light actuator/switch) was slightly askew. The hood would latch, but since the latch was out of position, the light switch never disengaged. Makes sense that this light would never show a draw as I would disconnect the hood light at the bulb connector since I had the hood open testing for current draw. Crazy stuff, but I learned a lot from videos like this one. Hopefully, my story helps someone out. Thanks!
Good share. I have a Lexus gx470 and still has current draw. I did the Eric the car guy method and put the meter in series with the negative cable and pulled all the fuses and nothing changed. So I’m a bit lost. I’ll try humble mechanics method soon
@@stallion78 if you have a draw with all the fuses pulled then I would next disconnect your starter main Cable and alternator main cable. I’ve had both of those cause draws on higher mileage cars. They corrode internally causing a faint connection to ground. Also people forget that a dirty battery case can cause a very small draw. Voltage can travel all the way across a battery top from post to post. It’s rare but is possible
H! my brother-in-law just prior to shipping out to Viet Nam placed a light in his trunk so you could see at night while in the truck Turns out the light was not going off after my sister replaced the battery commandeered her father, my dad who failed to find it. I think they accidently found it somewhat like you did. WHO KNEW? LOL
Very good investigative work!
I did something similar decades ago on a car that kept killing batteries. Turns out the glove box plunger was askew and the glovebox light was on even with the door closed. Took hours to find it even though I knew it was a light issue (couldn't see the light in broad daylight)
This guy was clean shaven when he started looking for the draw.
😂😂😂😂😂
J C , oh now! He is just trying to help you! Lol!
Then his video is misleading. He said it can only take you 5 mins lol.
Ha ha ha ha,thats no shit,you could become a grandfather looking for these things sometimes.
Your comment was worth the 10 mins I wasted here. Cheers.
I've been a master tech DIYer , weekend warrior, shade tree mechanic , jack of all trades master of none, under sensai mr Miyagi, for the past 30 years never ever seen such a great great video'. Thanks!
I've been a master tech for 25 years and never once did I think about physically latching the doors etc. And this is a great method for finding gremlins. I'm glad I found this channel, as unusual even as good as I am in still learning! Awesome video
Right on!!!
Yeah ok, and then there's most vehicles whose switches are NOT in the latch.
Furthermore if you've got a drop across the fuse, there's a problem with that fuse.
Sleeping vehicles should not be drawing unless you've got a module that's not going to sleep either because it's bad or somebody wired in (added) something wrong which is what I see all too frequently.
ua-cam.com/video/6xFo_oHFF48/v-deo.html
@@rjbradlow pretty sure I didn't need the lecture. And testing for voltage drop is easy. I'm not sure what you've been working on but pretty much everything made in the last ten years has the switch in the latch. Wondering why you're replying this way to my comment, seems to me you either have a problem with the video, which I didn't make, or me personally which makes you a bit of a child
What are grimlin, oh god 😳
Yup...latching the doors will help with de energizing any accessory relays,which can backfeed a circuit, giving you false positive readings..
I've been a tech for over 25 years.
I thought I was pretty good at electrical diagnostics.
This video set me straight.
What a great technique.
Thanks for these videos.
I wish these were around in the 90's.
Always keep learning man. As you know it’s how we stay on too
@@HumbleMechanic About to buy an 06 without radio. Owner says radio is killing battery. Great video! Does replacing with aftermarket radio fix the battery drain issue?
I am a 12v technician at a car audio shop. The number of dealership techs that don't know how to do a proper current draw test is mind boggling. I get a couple cars a month that are misdiagnosed because of poor electrical troubleshooting. If every tech watched this video the world would be a better place. And if you do this for a living Blue Point has a tool called the Amp Hound which does the fuse type current drop for you so it speeds up the job and makes you more efficient.
I’ve used this method with success several times. I’ve recently learned an extra hint to go along with this test. Prior to testing each fuse(especially with vehicles with a large amount of fuses), use a thermal image camera to look at the fuses. The one with the draw will show up warmer than the rest. Helps pinpoint the circuit quickly.
@You Wish I don't think so
Yes. The Caterpillar brand phones have FLIR cameras integrated with several models.
Valid tip but most don't have one. However, many have an infrared temp gun. Not as quick and easy but it too can point you in the right direction quicker.
Lmao I see new thermal scope in my future and tax write off.
@You Wish yes
Some of the new fuses now don’t have the test spots on the back because engineers decided that was too handy and they pride themselves in making things more difficult for us mechanics. Great video man
Never blame engineers....always blame bean counters
their ideal aim is to make things impossible for mechanics & diyrs, but the right to work attorneys need to pass a law that requires all favtories & dealers doing this to admit before sale, that the buyer now has no choice but to go to the corrupt, triple priced dealers every time- the headline of this warning should be, WARNING: we now own your S. 👋😒
I have seen test points extremely corroded esp living near beaches, I wonder if sealed fuses just make better sense. Only seen a couple, but some have corroded into fuse plastic. Never caused me issues but something to wonder about for small fuses especially
Some aren't really engineers, just placed candidates with a title and degree. !!
I'd just get new fuses. You can get enough fuses to do your whole car at the junkyard for $2
Had a draw on a skid steer. Not as much out there for help with equipment as there is for automotive. A fuse panel is a fuse panel so I administered your test and used in line amp draw method. Ended up being a bad starter. Thank you for taking the time to share the knowledge
Stewart W - was the starter drawing current when it was just sitting unused ? I know the old cars voltage regulators would do that at times. Was it a bad solenoid \ relay staying partly closed drawing current?
Best parasitic draw video out there. One note: good test leads are not cheap. If your multimeter does not read zero ohms, Fluke says that is just increasing resistance as the meter electrical contacts, and the lead connections get dirty or corroded over time. If cleaning with contact cleaner, or isopropyl alcohol doesn't work, you can use the "relative" button on the meter to adjust for the increasing resistance. Set to ohms, touch the leads together, push the "relative/rel" button, and the display will read zero. Fluke says you only need to throw the leads away when the wires become exposed, or broken.
This guy is easy to watch and always adds little touches of experience that simply following an instruction manual doesn't give you. Always good to see a Humble Mechanic video appear in my Google search results...
When I worked as a diesel mechanic it was always aftermarket shit. Even high end GPS trackers that were tamperproof. Always start with aftermarket add ons.
lol, i haven't started to trace my problem yet, but i know it is probably the cheap aftermarket radio
I feel we are blessed to have you and several others on UA-cam sharing your knowledge with us . Those who do not wish to learn and those jealous of your knowledge and capabilities will always try to discourage others . I am 51 and wish training videos like yours were available when I was in my teens . Truly truly helpful . Thanks for all your work .
Where can you get a thermo product and what type to have. And thank you I was thinking about changing all the fuses 🤷🏾♀️
@Get on the cross and don’t look back Amen
Don't watch he doesn't know what he's talking about. I know him personally and he's a fraud
Where do I find the link to the tables in this video 8:10
Electrical Engineer here; didnt realize that fuses has a large enough resistance to them to detect a significant enough voltage drop to calc amperage off of. Interesting technique. Thanks.
They're meant to melt at certain current. So it would have to be resistive to cause heat, thus generating voltage across it prior to meltdown. Even copper traces on PCB's have significant enough voltage drops, thus we utilize Kelvin connections. 😉
One small correction to note. 1006 in speaking of amps is 1.006A not .1A, simple mistake but for students it could be detrimental when they are struggling to understand 1000mV is 1V ect. Good video, glad to see other putting things out like this to help promote the industry.
Absolutely!
..."mil", meaning Thousand. ; "milli", meaning Thousandth. 1000 One Thousandths equals One(1); 1000 milliamps equals One(1) Ampere.
@Get on the cross and don’t look back Nah...just live and get luvs
@Get on the cross and don’t look back You are using the wrong scripture for your audience. These people are dealing with electrical issues. Try, John 8:12 “Then Jesus spoke again to them, saying: “I am the light of the world. Whoever follows me will by no means walk in darkness, but will possess the light of life.’
@@Mark-gg6iy Did you even read the replies? I was simply having fun in response to another person’s post.
You have been reported.
@@Mr_PNW yeah, bet he didna need no god damn fuses!
Great video and information. I personally disconnected the battery + and put my amp meter between the plus and the plus cable (10 A setting). I looked the doors and after the car went to sleep I saw a parasite draw of 250 mA. I reconnected the battery locked the doors and checked every single fuse like you did in the video. No draw found. I disconnected the battery again and hooked everything up like before. Then I disconnected the alternator lead from the alternator and the draw was 25mA. So my parasite draw was from the alternator. Since the alternator in my car is not fused I wouldn't be able to find the fault with your method alone
For new viewers, just an observation that 1006 milliamps is just over 1 amp, not 0.1 amp as was said at 7:06. Humble Mechanic has acknowledged that he mis spoke in old comments below.
Thank you. I was so confused.
I noticed that too. I'm glad to see a confirmation in the comments. 1 amp is not a small draw!
@@realSamAndrew But the mentioned discrepancy was .006, The remainder of the equations faulty fraction representation. And if this is the only fault in the presentation, of which the methodology is not just out of box, it ate it, Dude is batting 999.9? Divergent thinking is the undercurrent of innovation topping it off with someone who will actually show it to anyone/everyone? RARE!. This is better in so many ways and probably some I am not seeing . Props to ya and thank you HumbleMechanic
Ludicrous speed, I agree with you but you missed the point of my comment. I am not even concerned with the roundup which didn't strike me as an error. It was a typo which turned out to change the scale. It made a fairly insignificant amount into a huge serious amount. It also would lead the viewer to think that he was doing it wrong if he got a different answer. The rest of your comment is spot on the method is fantastic and the presentation was fantastic. Accuracy was the only small item and by correcting it it makes the video much better not worse. I am grateful for all sincere helpful comments and mine was meant to be that as well . I Thank the other commenters for pointing this out and also everyone who adds other helpful information
@@realSamAndrew I didn't even see it that way. It felt like just another comment section "stab you in the back to boost my ego" if you follow. I see it so much in videos where the maker is helping everyone and people say the most asinine shit and sometimes I feel compelled to say something only because it seems like the right thing. WOW the world would be so much better if we could all chill the hell out and simply be civil with each other,most of the crap is just misunderstanding anyway. THIS TIME I'm glad it was my mistake! Unfortunately most of the time I'm not mistaken. Nice bumping into you!
Its very important to check fuses before start metering. If a fuse is blown you might have 12v on one side and ground on the other (through a windshieldmotor or windowheater etc) and your multimeter might get damaged when measuring up to 300mV. Set meter to 20v dc atleast and do this test before switching over to 300mV.
I've done that mistake several times. My cheapo multimeter just says it's out of range. Nothing happens to it
Maybe there's still someone out there using analog meters though- those will take issue with 12V into the 200mV range 😉
Qualified automotive electrician for 15 years and have never seen this method before! Seems way superior! Never too old to learn something new 🤙 cheers!
42 years as a mech and never knew this. Thank you!
Ran into problems trying to do parasitic draw test after watching videos where they pull the fuses. Aside from forums (TDI Club, VW Vortex), this has been the most straightforward explanation on how to see if anything is draining my battery. Thank you!!
Car newbie here. I was super excited to try what you talked about. I had to do several adjustments and it took me quite awhile to understand everything, but I found out I had such a huge draw by my burglar alarm I had to adjust my meter up to volts from millivolts to get reading. I sure hope you have a video about this now. Thanks, a very informative video.
I've tried to explain this technique in words to people on a number of occasions, but they generally do not get it. Thanks for the excellent video.
As a vw master technician myself, this has always been useful. I now work for audi, been there 3 weeks and taught my shop foreman how to do it this way...he was so confused at first lol then he made sense of what we were looking at. He found this easier.
Can you help me out? I can't find the shortage
@@josejrsilva4054 this is for a current draw not finding a short.
@@vduber03 It might still be useful. ...If Jose had a 'dead short', then he'd know the faulty circuit by the fuse blown , however , if it's a partial short , then it can be a low current leakage and isolated as shown in the vid. If he does have a dead short then replacing the fuse with a mini circuit breaker breaker helps in the diagnosis procedure .
Oh my lord! Great Video! Didn't even think about 'putting the car to sleep', Thanks Charles! My wife's 2007 Toyota Corolla is suddenly draining the battery if not driven every day or two. Replaced the battery, did the 'disconnect the battery cable' parasitic draw test and found only about a 30mA draw. Charging system 13.4-14.2VDC, no idiot lights, however I believe it's the OEM alternator (only about 78K miles)...so still not ruling the alternator or regulator out. But never thought about latching the doors and putting it to sleep...outstanding advice.
I have a 2004 Chrysler Crossfire. Over the last few years two seemingly unrelated things started to happen. The first was that when driving on hot days - say more than 33 DegC [91.5 DegF] - the Security Alarm would start and would eventually stop after lifting the bonnet (to cool things under there down). The second was that the virtually new heavy duty battery would not hold its charge more than about a month or so. I finally decided to address them with the battery-drain being the first; and, following this video’s instructions to the letter, found that all fuses gave less than 0.1 mV EXCEPT the one which combined the interior roof light, the boot light and the Anti-Theft Alarm Unit, which gave a reading of 0.6 mV. Upon disconnecting the Alarm Unit the reading on the fuse (No 9 in my car) dropped to 0.1 mV. Obviously the Alarm Unit has a fault, which I’m going to follow-up. So, THANK YOU VERY MUCH “The Humble Mechanic” for your really useful method of finding battery drain problems. In my case it’s solved 2 problems at once!! 😊😊
great idea and great way to do a parasitic draw test. However, i will suggest(after doing all preliminary work you did with latching doors and hood) use of a clamp-on probe on negative side of battery with arrow facing away from battery and if you read any Amps then you have a parasitic draw. then you do same in positive cables and when find which positive cable has the draw then trace it. if it goes to front distribution box then you do voltage drops on fuses as you did and go with the chart(great tool by the way). if positive cable goes to rear distribution you do voltage drop there and no need to waste time doing front or side or whenever the distribution can be. Modern cars have 5-6-7 or 8 boxes with fuses so will be a great idea to focuse on the power wires that supplies those boxes. when you find the draw on the fuse through volt.drop then you need a wiring diagram to see what that fuse powers because can be 3-4-5 different components. after you find diagram start unplugging one by one the components and when you do so on the bad one you hit the lottery and and your fuse will change reading to 0V.
Good post. In the electrical world we called it divide and conquer. Keep breaking the entire system down to isolate the area. Then once in the right area ( fuse box #XX) do individual testing until you find the draw. Then Bobs your uncle.
what arrow are we talking about (arrow facing away from battery ?? )
I learned a few things for sure. I always test my leads before checking continuity, or ohms. Didn’t think about checking them EVERY time. Solid advise though. Sometimes it’s the little things that will drive you mad.
Just had a bad battery on my F100 that passed a charge and load test because it was literally the first thing I checked when my truck wouldn’t start. I knew I had a dead short somewhere. No off gassing, no swelling, no amp draw on the terminals, or fuse box. Truck would not start with a jump. Tested ground cable, solenoid, starter, positive cable, starter cable. Replaced parts that looked sketchy, serviced others. Took a few Saturday afternoons to find before the battery finally stopped taking a charge. Put a new battery on and all problems went with it. Apparently it was only shorting bad enough when I went to discharge it by starting. Otherwise it was powering everything else and showing 12+ volts after a charge....until it didn’t. Let it sit for 3 days to verify that draw was gone.
I had a bad battery connection that allowed all electrical components in the car to work but not start or start poorly. Once the connection was fixed, no problems. I wasn't suspecting a loose battery connection since headlights, etc. were fine.
Thank you so much for this video. My daughter's '06 Beetle convertible developed a parasitic power drain over the past month or so. Following your procedure I narrowed the power draw down to fuse 38. Driver and/or Passenger Door Control Unit. After sitting for 2 hours, fuse 38 was pulling about .8 amps. We had an issue with the driver side door about two months ago where the window wouldn't drop sometimes when opening, and then it wouldn't go back up. Dealership diagnosed it has being out of adjustment. It has been performing normally since then. Before locking the door mechanisms for the diagnostic procedure, I decided to remove the driver side door panel so I could have access to the window motor connector. After two hours of waiting, I verified there was still an approximate .8 amp draw from fuse 38. I unplugged the window motor and the draw went to 0. I plugged it back in and it went back to .8 amps. I may be mistaken, but I think I smelled a slight burnt smell from the window motor control unit when I unplugged it. I think this is the culprit. I am going to order a new motor tomorrow morning and see if this sorts it out. Thanks again!
did it work out ? 800mA is a high draw, and sometimes the plugs on those regulators suffer from high current melting them a bit, so you can see where it's burnt and the plug may need replacing too.
@@DeepakKumar-lv4te yes, we replaced the window motor which has the control module built into it. The current draw stopped, and no more issues with battery drain.
Best video I have seen on this. Working on a kia that we just cant figure out. Changed starter, alternator, battery, power steering and pulleys. Still having draw and cold weather starting. Thanks for the resource.
I wish I had seen this before I went through our bucket truck and started replacing parts...After spending over $2,000 on parts, I finally did this test and found out that our power inverter was the problem. A $2 external power switch, and problem fixed. Thanks for this video! My fault for not googling this before hand lol
Thank you so much for this. I have been trying to figure out how to do a parasitic draw on my homebuilt aircraft and none of the aviation sites were any help. I've been looking for exactly this info for weeks. Seems so easy once someone explains it to you. I appreciate you taking the time to post this.
Many thanks for the phrase easy to see when explained/ true even for experienced/ informed person. I have been an electronics technician since 1972.
Learned something new today. Used voltage drops many times before for troubleshooting but never thought of using it to find a parasitic draw. Great video!
A fuse as a power shunt! Never thought of that until now, but makes perfect sense!
Not a techie myself....but I learned 2 things , er maybe 3. How to check the fuses with the probes , how to check my ohms reading on my voltmeter. And to hold on to my 2005 Highlander because it's not as high maintenance as the car you were checking...lol...P.S. ...great presentation . You stayed on point in a highly technical subject . You didn't waste time with lengthy introductions . The length of the video was about the optimal time I want to watch. Others spend 20+ minutes and don't deliver as clear and concise info. Great job.
For older cars, you may have to tape the door ajar button on the door frame instead of flipping the latch.
I was wondering about that. Thanks for bringing it up.
yeah and I don't think even duck tape could even keep em pushed. those things are buff.
@@jeromeneely202 I jamb a toothpick in along side the plunger to hold those buff ones in.
Thank you. This is the first video (that I have seen) that is accurate and considerate of late model diagnosis. Thank you for stressing the importance of leaving the fuses in place. You briefly mention the interconnectivity of data buses and how one module can wake up another module. You should expand on this in another video. Maybe talk about a draw that is caused by bus activity. A basic video on isolating busses. Sometimes ALL the fuses have high current because nobody goes to sleep. Maybe too complicated for people that aren't techs, but so important for young techs. Again thank you
Thanks for this quick tip, particularly about verifying your probes before beginning to test circuits. That alone is worth the price of admission. As DmcHartsoe pointed out, you might want to say something in your notes, or add something in the video, about the math issues relating to the proper identification of tenths, hundredths and thousandths of a volt in measuring the typically very small voltage drop across an active fuse.
great video , just remember to always make sure your diagnostic scanner is not plugged in and also make sure that key fob is far from the car as this can make some car systems to stay awake.
Ive always done amo draws pulling the fuse. I didnt know it could be done this way… thanx for posting
Hey, before you do any of this. Sit in your car and lock it, keep your ears open and listen for anything or keep your eys out for anything. I heard a thump consistently coming from my driver seat. Turns out my ice scraper was pushing my electric seat back and it couldn't go back any further. But this is the same for something like a stuck hvac actuator clicking or your info screen not turning of cause a fault in your ignition switch. Sometimes it will help you find what fuse to pull durring this test
Wow, I been in the trade for over 40 years, I have a lot of experience with auto electrical and diagnostics and I still learned something today. Thanks for taking the time to make this video.
I must admit I generally click on these videos to pick holes in them and occasionally post comments on what they are doing wrong if it is extreme and obvious. :-)
Nothing to pick on here (apart from a wee math error :-))
+Stambo hahaha. This may be my favorite YT comment of all time. :)
Stambo Yeah ironic isn't it the old method for me has been working for 35 years but it's always good to know something new
Wow, a UA-cam professor that acknowledges his motives. Never understood what the draw is of basically acting like the know it all each family has that we avoid like the plague and talk shit about whenever his name comes up.
probably because no one does this , im not a mechanic but i am electrician and long time driver , never saw it . If i had to do it , i would check across the battery
I have Citroen c4 grand Picasso 1.6hdi semi automatic after shift could not get reverse but managed to drive home I notice while driving service light keeps flashing what could be thaEexact fault
I've seen this method before, I've actually printed off the charts from power probe myself. Had a company training trip to Lincoln tech in colorado, the lead electronics instructor taught us this method.
If you do this method to the main battery fuses you can also pin point which fuse box is the problem. Each big fuse goes to a fuse box so you can eliminate probably 80% of the potential problems by measuring 5 or 6 fuses.
True but the big fuses have covers on them and are not like the small ones with the metal contacts
Well done! No extraneous talk, just the facts 👍
Basically you're applying the principle of a "shunt" normally used into voltmeters and other devices to measure current. Well done :)
Great info. One thing to keep in mind if you are looking at older cars, at least through the 1980's with American cars, the dome light switch is in the door jamb by the hinge so closing the latches wouldn't make a difference. Then again, those old cars you could just pull a bulb or two and be done with it.
Yes you have to tape those down.
Some cars has the door jamb switch as well as the latch switch. These circuits are more complex due to alarm systems and to tell the computer that the latch is activated.
My 1995 Sentra dome light has an off switch (and nothing else comes on).
Great video - even as an electrical engineer I didn't know the fuse voltage trick! But a slight misstatement regarding your first chart reading - you had a current draw of about 1 amp, not .1 amps as you said.
you beat me to it
Great job. Some things I didn't know. I remember we used a test light, before the meters. I miss those days. I was the third generation working in a auto electric shop. we started in 1936. And sadly ended in 2006.
Ive checked for parasitic loads many times but didnt consider all these subtle things. Learned a lot.
Me “car” is the new house batteries in a C-class RV that would alarm low voltage when used overnight after a full day of driving / charging. This will be a great help! 👍🏻
I wish they would have had something like this 30 years ago. Now I'm to old to do it for the most part. Great stuff
Found your channel through engineering explained and couldn't be happier I did. I love learning as much as possible about cars since I do all of my own maintenance as well as repairs when I feel confident enough in doing so. Looking forward to watching as many of your videos as I can thanks for what you do for us.
Electronics tech here...might mention that it does take a pretty decent meter to get anything like a semi-accurate reading when getting down into the low mV range. If you are considering trucking over to Hazard Fraught to shell out a whole $10 on a meter, you will certainly get what you pay for. IMO, everyone ought to have a decent meter that they can trust, so maybe a used Fluke on eBay or a Owon or Triplett from Parts Express. Stay away from the $10 stuff.
VERY good point!
Jr McDonald - While I totally agree on the quality of the equipment/tools. The fact is that in real life car workshop environment a top of the line ($$$) is a pure waste of money. You want something cheap and simple, that someone will trow a wrench on top and you don't get an hearth attack to see the dollars flying out of the window. Don't ask. LOL :-)
With this said the need for very high accuracy in most car testings are not even close to a electronics repair lab counterpart. Some 98% of the work is just like in this video. It's more important to keep the lead tips clean and tested.
So, not the $10 for sure, but the $20 should be just fine. ;-)
Yes I agree. BTW the cheapest Harbor Freight multimeter will accurately measure down into the micro volt range with complete safety.
Go back to grade school bud.
Jr McDonald ever open one of them 10 dollar suckers up to see what Fry's them? Pretty scary shit. I wouldnt use them on High voltage. Might be your last test.
But they make a good door stop in a pinch.
Thanks for this method much better than the pull fuses method (which works) that takes soooo much longer as you have to wait for the car to go back to sleep upon reinserting the fuse. Absolutely brilliant.
My silverado has a screwball terminal style where it screws into the battery. I had no idea how to do a proper draw test with those, but you gave me a solution. Kudos to you, my good sir 👏
Great video! Basically you are measuring the the voltage drop across the fuse just like measuring across a resistor in a circuit. To take it further, if you don't have that handy chart with you, you can always remove the fuse, switch to ohms on meter and use ohms law (V=I*R) to figure out the current draw. It might be a little more accurate as you have real numbers to calculate. Use the battery voltage and divide by resistance. This will give you current in amps. I personally have not used this method but I see that it would be far more superior than other methods. Math never lies. :) Now I am tempted to go to the car and document every fuse draw and save to a list. So if there should be a problem in the future, I know what circuit values should be. Thanks again.
is that asterisk a X? lol
Parasitic draw is everywhere these days, especially when our cars become electric. Thanks for a nice video
Remember, some modern vehicles, as well as most older, use a door jam switch separate from the latch that activates the dome lights.
yeah I have to jam mine, it is 1991. I dare not latch the doors open it will have a fit. Have to close doors and leave drivers window open.
I tell you what a light with two leads can be really handy finding a short to ground. Hook one side to battery +. Then start by pulling out a fuse. Connect the other lead to the + side of where the fuse plugs in. Do that with each circuit. If the light comes on you have a short to ground in that circuit between the battery and the fuse. When the light goes off the short is fixed or just not shorted out. You can use the light and jiggle stuff, close doors, etc to see what causes a temporary short. I did this to isolate a short in the passenger side back door. A yellow wire to the window regulator had missing insulation and would short against the door sometimes when it was closed.
You’ve made a hard problem easier. Thank you. I’ve watched 20 videos to get to suspect problem.
Best explanation on this subject I've seen! Especially like the attention to detail, and memory precautions on taping over the doors in locked positions so you remember NOT to close them during the test. Excellent, sir, excellent. It is noticed.
Thank you
I do that on a hatch lid to allow the lights to shut off when using the back accessory outlet for charging, but I don't trust myself to notice tape so I put a small block of foam across the latch to keep the bonehead from closing it onto the striker.😜
Thanks, I’m swapping my radio and this is exactly the technique I was hoping to find to see if the new head unit has a draw issue.
You covered this topic very well. Since I don't own a German made car, I love these videos that cover "all makes" .
Awesome! Thank you :)
This gentleman is excellent, voltage drops rule , sometimes calls I R drops
, because E= I x R , which is Ohms law , which all you have to know to control electricity learn it love it , I love a large current draw , the sound , the heat , the sparks
"Always check the leads..". Sound advice thanks.
Used this method before with no luck.I found the car security system picking up movement,and triggering the alarm System,As we know Modern Security systems are not easily disconnected,they also have internal batteries.
Wow! What a great find this Humble Mechanic is. I'm a fairly good mechanic from years of fixing my own cars, but always learn something new and very useful on this channel. Great explanations, no wasted time! Thank you!
Thats exactly how I check for a draw. Nice work.
This video was extremely helpful. The guys at the auto shop couldn’t troubleshoot the problem and I had 3 weeks to wait to get it in to the dealer, so I did this test myself and found a failed rear wiper drawing current.
Thanks for the help!
this is a great way to check parasitic draws on vehicles and is also great to find dirty connections that can drive you nuts , such as a bad ground problems . same test just a different way to look at it such as from your ground on your battery to any other grounding point that might have a problem
Can you make a video just on how to use a multimeter PLEASE
"Humble Mechanic," you humble me. Great video!
Thank you
Humble with a touch of sarcasm hmm
7:05 Where did the 35mA spec come from that he speaks of? Also, aren't there some things that are supposed to be drawing current at all times like the receiver that listens for or detects you key fob, etc.?
New scenario, but happened to me.
My body control module was getting wet. Sometimes the AC would not shut off when the car shut off, or the sunroof switches would not work, or other window switches, or.. even the interior lights would not shut off 100% when the doors were closed and the vehicle was locked and alarm system on.
My mechanic said it was each system failing, but my carpet being wet told me otherwise. I was shown how the water might have been coming into the car, so I resealed with silicone. FIXED! No more wet carpet or funky electrical draws.
Thank you. Great video. I am an Engineering Tech and never thought to measure the fuse drop to calculate the circuit current.
I learned on older cars where you start pulling fuses. This actually makes a lot of sense and I can see where it would be very handy. Thank you.
Chart not accessible with link anymore.... Came to this video with doubt and ready to blast you in the comments but left with a little more wisdom. Thanks for this great information! I do electrical work on hotrods and this will be my GO TO method from now on!
Is now, I just got it and copied out.
Thanks for the video! I've been chasing a parasitic draw down for awhile now and this video made it easy to locate! Thanks again man, you're a life saver
These are great methods! Will try it tomorrow. My Mercedes has two batteries and I havent found an instruction how to troubleshoot that, but your method does not rely on battery disconnection. Great!
Of all the videos I've watched, I think this guy shows the best way
I've been doing this without the charts, then going for the circuit with the biggest drop. Thanks for the charts! At first glance I wondered if they actually measured these values, or whether they used Ohm's law, calculating the numbers. A quick back-of-the-envelope check on a couple of chart numbers shows variable resistance depending on amperage, although strangely resistance was lower at higher current for a few. The numbers are really small, so slight corrosion at the tip of the probe might change values. I like your idea to trick the computer into thinking the doors are shut so it will go to sleep.
W
I would expect a lower voltage drop on a higher amp fuse, after all it does have to carry more current requiring a larger internal fuse element. bigger element carries more currrent without overheating, ie blowing out.
It's not that strange to find lower resistance for the higher rated fuses. Fuse is meant to blow at certain heat developed by current flowing across a resistance. Heat is generated by power dissapation in the resistive material. Power is the current squared x the resistance. Simplistically speaking, if you had same resistance for the higher rated fuse, say 30A, that fuse will blow just the same as the 1A fuse. Of course, they can use different materials to change characteristics of when the material melts with different resistance/current combo.
I had a parasitic draw for 26 years, then I got a divorce.
Oh snap
I heard that when you get rid of it, it draws half your battery power
Hahaha...zing!
@@ismoketwojointsbeforeismok5882 yea, and you'll never Get it back either.
lol
I'm not going to lie. Most of the cars I've seen with a draw are being sucked down by improperly installed gizmos like big sound systems or aftermarket remote starts. You would not believe the rats nest fluster clucks some people leave under their dash.
Travis Callahan Just a note on batteries: unless you are using the car daily, you're going to have charge loss that takes its toll on battery life. Sitting at partial charge will allow sulfation to develop, and the the battery will hold less and less charge; a catastrophic scenario. It seems nit-picky, but it is true. A good battery maintainer is a smart move. A battery in a car without electrical power-assisted accessories will last quit a bit longer than a car with all the powered accessories.
Lou Fazio - I held onto two extra car batteries for four years by keeping them each on their own maintainer and they still worked great when I finally used them in my car. kind of morbid but I tell people a car battery is like a person the longer they're dead though less chance you have of bringing them back to life. sulfation is a huge killer
not sure what that has to do with my insight but yes batteries discharge over time. but it takes a really long time, unlike a draw that can sometimes drain your charge in a few hours.
Travis Callahan If you're talking to me, I'm saying that battery self-discharge of more than 1 day will begin enough under-charge; adding parasitic load is additional (intentional parasitic and not unintentional shorting). Concerning rat's nest wiring and typical installations, ground loops are beginning to be a consideration for more delicate electronic's connections near larger amperage flows e.g. steering wheel control add-ons for after-market stereos.
civicturbo2009 I'm a big believer in this now. It's just that my previous maintainers always seemed to die out. I'm trying the resonance desulfation (BatteryMinder) now.
A clamp on DC amp meter can't be beat for ease and quickness for finding where a parisitic draw is happening. It takes a little understanding to figure out how to zero out stray magnetic influences that affect the readings but it's worth learning how. A chinesium clamp-on DC amp meter sells for less than 40 bucks on Amazon and every auto mechanic should learn how to use one. They can save a LOT of time!
I have a "couple steps better than cheap" clamp on that comes in very handy, though I'll be replacing it ASAP with a good Fluke unit to augment my 87V.
Wow ,good advice for the volt meter and the leads. Your special Charles and I appreciate the gift of having you. Pesce, respect, blessings in abundance to u and your always my VW car go to guy . Humble indeed
Nice. Never thought to check the voltage drop across a fuse. Thanks
this guy never blinked once
😅😂
Oh wow, the suspense in automotive diagnostics. The dealership, the manufacturer, nobody knows... As soon as you find the problem that everyone is having, it's gonna be a different diagnosis on the next with the same code......
After I saw this comment, I watched again, and you’re right. Maybe he just kept blinking at the exact same time I did?
Thank you, this video was really helpful. (Took me a while to realise I needed to press the open door button on the remote to get those door latches open again though!). I have found the parasitic draw now, it's on a fuse for the ABS and Parking Brake control module. Now what....how do I proceed? Have you got a video for the next step!
Excellent. I wouldn’t consider 10 minutes time consuming, compared to not finding the problem, or going down the rabbit hole in the wrong direction.
EXACTLY!!! (and thank you) Some will chase an issue for days rather than learning something different.
Thank you.
I learned a new way to test WHERE a Parasitic Draw may be....but not wheyher there IS a draw.
Great video. Been wrenching for 35 years and never used this method. I know it works though. I use a tool called Amp Hound. It calculates the the draw for you.
Explain
@@Nick-fy7yi I'm old school. Did battery draw with a test light between negative cable and ground, then pull fused till light goes out. This method doesn't work with new cars. Amp draw on each fuse is more precise. There is a tool we use at work called an Amp Hound that does the calculations for you. It works great.
@@tomcisneros5965 yeah I’m in Canada looking for a amp hound can’t find it . My battery is having a parasitic draw and I can’t diagnose where it’s from. Never used a meter of anything before. Brand new battery.
@@Nick-fy7yi I don't remember who makes it , but if you Google Amp Hound it should come up somewhere. In the States you can find it. I don't know how it is there. Try your local part stores as well. You may even find a tool close to it if you ask your parts guy. It's very user friendly.
@@tomcisneros5965 thank you
If I wasn't already subscribed and I saw this video, I would subscribe. Great resource and skill.
+briansmobile1 thanks dude!!! Hope all is well on your side of the world.
Well I wasn't subscribed but I am now :)
My thoughts exactly, I now watch this man and scott kilmer. This man explains how and why things happen .Scott gives more of a comedy but both of these gentleman know what they are doing .Fixed couple cars by looking and watching these gentleman
@@robertodom9145 you had me with you until you mentioned Scotty Kilmer lol
I saw this video and I did subscribe.
I’ve just bought the Wife a mint, very low mileage 4.7 Grand Cherokee for Christmas that four days into ownership has a flat battery.
I’ve got a new quality battery for it, but I want to find out for sure if it was the old battery that was at fault, (likely, as it won’t fully charge), or it has a parasitic current draw that’s going to leave us with another flat battery.
Best video I've seen on this. How do you find those nagging intermittent draws that don't show up on this test?
Use an amp clamp with min/max set and APO disabled.
One of the best produced, and informative videos I have ever seen. On any subject.
831 people don’t appreciate how good your explanation was thank you
thumbs up for power probe charts and humble for posting the info. Thanks
Rock on@
Very useful info. I have a 2007 Silverado HD2500 crew cab that goes down after a while. It's got two new batteries so there's some parasitic draw happening. This might help figure it out. Thanks.
If you find it out I have a 2005 GMC 8.1 HD2500, same thing happening
I have a 2006 duramax goes flat in 2 weeks, did you find it. Im pretty sure i traced it to factory stereo, i will know more in a week.
I have an older Chevy 2500hd 2003 with what's weird is when I bought the truck from my son he didn't mount any trailer brake controller, already in there. But, wires for controller ran from engine compartment to cab through the drivers door above the top hinge. I though this was a rather crude way of running wires from one area to another. But who am I? After a couple months of sitting many times a flat battery would result, and also, this truck has nothing electronic other than aftermarket radio. Crank windows, manual seat. My close friend uses battery tenders for all his battery powered equipment, unfortunately that would hind a problem, like my 2002 honda Forman rubicon 500 for instance, I keep that on tender all year, especially in winter when I need it to be reliable for snow plowing. The honda has a tendency to have a hard time winter starting with much cranking, hence, battery tender. I did change the way I start it though, I choke and push throttle few times, and then turn over with no throttle for 5 seconds trying to create vacuum. Then resume cranking with just plain choke no throttle, fires up. . After charging I will try this, thank you.
very good video and useful information
Very cool. I am amazed that cheap fuses have very similar resistances and also that someone has measured it to make that chart.
Okay, so now it seems so extremely clear how to "close the doors" without actually closing the doors. My EOS has (2) 6V batteries in the trunk. To close the doors, she sat in the back seat to read the MM with leads through the armrest opening.
The lead's probe came off of the terminal and for about 5 minutes, we had NO IDEA how I was going to get her out!
Then it came back on, so I guess it had temporarily lost contact but came back (it was taped to the top).
So dumb, but never again. Thanks for including the latching of the doors, trunk and hood in your video for the infrequent DIYers out here.