Retired electrical engineer. Your explanation is spot on. Ohms law says it takes 1 volt to push 1 amp through 1 ohm. Every connection, piece of wire and anything else between two points is potential resistance. The rusty terminal caused the extra resistance in this circuit. The conservation of energy law says that energy cannot be destroyed, just transferred. With resistance, its's transferred to heat. As the temperature on that rusty terminal was raised, the resistance got worse and made the voltage drop worse until the point where there wasn't enough voltage to start the car. We saw this on the Honda battery terminal in your last video when you "let the smoke out". Again, spot on, perfectly explained and easily understood..... When your body gives out from working on cars, you should teach......🙂
Fully agreed! I, too gave up mechanics to teach at a mechanic's school. Did it for 18 yrs. Let me clarify Ohm's Law: Volts= Amps X Resistance. So, 2 volts will not push 2 amps of current thru 2 ohms resistance. Electricity is so easy, once you know and fully understand how it works, but it is a total mystery if you don't understand it.
I learned years ago clean everything like you are going to serve thanksgiving dinner on it like Bill Hewitt used to say. It doesn’t take much to reduce the pixies from flowing correctly.
I hope they put back the old battery and starter, nope just didn't tell the customer the real problem. I'd say you need to run classes to teach the techs around you but that would kill a revenue stream 😅
so, previous shop/s did the old parts cannon, including "a battery" and weren't bright enough to clean the terminals or see that was an issue visually? ay caramba!
I tried that test... I placed the screwdriver end on battery positive. Why did my screwdriver get red hot & partially melt? I gave it a good 45 seconds to see if it would stop. It didn't! Very difficult to remove the screwdriver, as it appears to have melted onto the positive post... Should I replace the battery now?
This is exactly why my headlights were flickering on my 2011 Silverado. Bad negative terminal at the battery. After a round of UA-cam voltage drop lessons, I narrowed it down and replaced the terminal end. Fixed the problem, and gave myself confidence that “If you can do it, I can do it.”
@@chuy1674 The battery terminal ends on those trucks are enclosed so you can’t even see the green puss taking over the cable inside. I couldn’t see it until I cut the cable off. But I figured it out with a multimeter and SMA lessons.
I had a voltage drop from battery hitting radiator and loosing the acid. Lots of soldering to repair the wire harness under the radiator. Used a lot of baking soda as well.
An old man's car died in the McDonald's drive-through. After pushing him out of the lane I figured out that it was getting no fuel. I diagnosed a dead fuel pump, and he said that was his third dead fuel pump in 18 months. But I also noticed on the computer that the car was showing only 10 volts when running. I replaced the fuel pump and his car ran again, but I also knew that the low voltage could be the reason the fuel pumps were dying. The very first thing I checked for voltage drop was from the battery post to the battery clamp, and there were my 4 volts, basically two volts per post. I removed the clamps and found both posts coated with something like varnish. I cleaned them and boom, 14 volts when the engine was running. Hopefully that will keep the new fuel pump from burning out fast like the previous ones. By the way, I'm a DIYer who learned voltage drop testing on this channel (along with most of everything else I know about cars).
that's called low voltage burnout. as the voltage decreases, current consumed increases causing premature wear. also why it is not recommended to keep cranking the starter when the battery is low. if you ever see a car keep blowing bulbs there could also be a similar issue. great job helping the old dude out!
Can't believe whoever went through the hassle to change that battery didn't take 2 minutes to clean visible rust/ corrosion off the clamp and cable. Also can't believe anybody else does a better job of explaining electrical diagnosis and trouble shooting than you do. Thanks and keep it up!
The video makes perfect sense, but the fact that they had the battery replaced to attempt to fix this problem without cleaning the terminals is crazy! Great job once again Eric!
I learned voltage drop when I was in trade school. That was a long time ago. (1984), Over the past 40 years I've only had a handful of times when it would have come in handy, but of course, for the most part I worked at new car dealerships. I'm semi retired now and I work on old rusty junk. These refresher courses on voltage drop will come in handy. Thank you.
New car dealerships typically see cars that are less than 5 years old. The built-up resistance usually follows after more years have passed. Independent shops see them all the time because they work on a range of old & new cars.
A most eloquent and thorough articulation of voltage drop consequences and testing. Well done, as always, Eric. Best wishes for continued success from Florida.
I really like this channel. 1 - you cover the essentials of being a mechanic in the rust belt. 2 - you cover what is involved in diagnosing and fixing modern cars. As you said once, it is all about the data. Thankyou Mr O and Mrs O.
One the days when I am feeling old, I point the FLIR camera at it after cranking the engine, and look for the hot spots. The voltage drop check is still more accurate and cheaper, though. I bought the silly thing to test cooling systems and catalytic converters, but ended up using it for electrical faults. Hotspot in a fuse box? Boom. Found it. At least it wasn't a total waste of money.
You make the testing process so simple, but I find myself disturbed by the fact that the "other shop" was unable/unwilling/not smart enough to do such a simple test. Instead they fired off the parts cannon for hundreds of (perhaps unnecessary) dollars. Then they send the car to you, you identify the issue, and they finally fix the actual problem and the customer ends up being oblivious to the fact that they've been ripped off due to that shop's incompetence/laziness/greed.
I think that junkyard paint on the light is telling a story. Perhaps one like that's how the body shop put it back together after it got hit in the front end.
Eric, a great tutorial. One of the additional challenges of looking for the trouble spot is finding a way to probe a connection point and the connected conductor. Over the years my collection of DVM probes with weapon sharp edges and a variety of file sharpened back probes has filled a shoe box. Surface oxidation of a connector or exposed conductor can be an additional challenge. BTW the insulation piercing adjustable needle probes made by Pomona are wonderful. I always seal the pin holes in wire insulation with liquid electrical tape afterwards. As you aptly pointed out ,every mechanical interface in a circuit is a potential failure point . Be thankful you don’t have a boat that is used in a salt water environment. Every connection point is a potential trouble spot. It’s beginning to look like this is the reason why the electrical system in the MV Dali container ship failed at a most inappropriate time. Dude, you are a wonderful instructor . With all the electronics in cars these days , an individual with a good basic understanding of electronics and electricity will be a superior automotive diagnostic tech.
Great demonstration! I typically teach a maximum of 0.1v per connection and 0.1v for every meter of battery cable. Never to exceed 0.5v for the entire insulated circuit or entire ground circuit..This only applies to high current circuits such as starter and alternator testing. I'll bet on that car if you cranked it for 15 seconds in clear flood mode you would be able to "see" a hot connection with a thermal camera. 1volt times 100amps is 100watts. That's got to warm up something...
In aviation, a 0.5V drop applies to any circuit carrying power not just the big ones. The tables in AC 43.13-1b go down to at least 22AWG. They also differentiate between continuous and intermittent loads. They allow a 1V drop for intermittent loads.
disable fuel/spark and crank until something emits smoke.... 🤪 even if manually via starter relay jumping. wait I would never do such a thing and have never( yeah right, look for smoke first, then troubleshoot second)
I learned the hard way too that checking every connection point also applies when checking for opens/shorts. I couldn't figure out why one of my TPS on the throttle body was showing 0v but everywhere in the circuit was 5v. Then by accident I pressed really hard on the connecter and the voltage came back, some how there was a failure from the back of the wire in the connector to the front of the pin, lol. I checked the voltage everywhere except the place it mattered, lol.
I'm a bad mechanic but have used this technique many times. I don't understand how the prior shop just decided to fire the parts cannon at this problem. What the hell?
Several years ago my wife bought a Chrysler Pacifica at another state car lot. (When Pacifica was an Suv type vehicle). It was low mileage great condition, optioned out and a great price. We picked it up on vacation on the way home. About 150 miles on the 250 miles trip the dash went dead and engine turned off. A call to the dealer who denied any knowledge advised to take it to a dealership. It was late afternoon Saturday so nothing open. I made it the rest of the way with no more issues. Now thinking I'd been scammed (deal too good to be true). I simply Googled the model and symptom and then answer was a bad connector on the hot cable from the battery connector to the fuse module. Monday I called the local deal to get a replacement. Of course back ordered with no known date. I measured the diameter and length of the cable, went to tsc and picked up a riding lawnmower starter cable that was the same diameter but 1 inch longer. I swapped the cables and she drove it for the next year and we sold it. We made a little over $4000 on that vehicle by replacing a $3.95 cable.
Eric, you are so right when you say that everything imposes a bit of voltage drop. One item that has to do this is the fuse. It relies on having a certain resistance so that when the current gets abnormally large the wire in the fuse will heat up and eventually melt. You often see a largish fuse (e.g. 15A) protecting a circuit taking (normally) only a few tens of milliamps. The fuse size is chosen to protect the wiring and also ensure that normal voltage drop across it is small so as not to affect operation.
For you auto restoration folks with 6 volt systems ( more common than you know ). The 6 volt systems are super sensitive to any corrosion. Internal corrosion INSIDE cables OR use of much lighter gauge ( 12 volt rated cables) will cause starting problems. Remember the GROUND SIDE of the circuit needs clean connection. CLEAN. ALSO as heat is generated by high current voltage drops you can quickly touch the cables and besides giving yourself a first degree burn can isolate the source of the voltage drop.
Disconnecting and cleaning all ground connections would be the thing to do if we don't know how to troubleshoot using voltage drops. Having the scope is perfect because we capture the voltage level when doing something like turning the ignition switch etc. Much nicer than using a VOM. The next best thing would be using a VOM that records min and max voltage levels.
Aftermarket systems installed on vehicles can cause a LOT of voltage drop problems in fleet vehicles. Then they became our problems when they didn't work right. Or when a three axle tractor with trailer had a problem with the OEM instrumentation not reading correctly and for several months the problem was chased. When the vehicle came in one day the dash voltmeter read in the 11 volt range. With the engine running, one of the two group 31S batteries read 14.2 volts the other read 12.4. Both batteries had individual positive and negative cables going to the starter. When the cables were checked by pulling on the cables near the lugs (terminal) at the starter one cable pulled out of its lug. It took a little work to fix it but once repaired both batteries read 13.5 volts, no more voltage drop and that repair eliminated all the electrical problems in the vehicle's instrumentation. YA. VOLTAGE DROPS ! ! Good one Mr. O!
When you have a problem like this and you got an old car the best thing to do is just go ahead and change the positive and the negative cables that will eliminate your issues and your your battery will hold the charge and it's a cheap fix especially if you do it yourself
I worked in electronics for many years do bench repair of PC boards and used this troubleshooting method all the time. Worked with many techs that would shotgun and sometimes finally got a fix.
This is how i fixed my son's car. Battery kept going dead. I knew it was a draw from some where. Watch a few of your other videos on voltage drop, current draw, etc. Knowing what circuits had full time power was a big help. Found the draw. What able to isolate the components. Found the problem. Thanks you for your help and breaking it down Barney style.
@@SouthMainAuto Nah, wasn't any help because I don't have any of those problems because I learned years ago that those aftermarket replacement battery post and cable clamps are crap and nothing but trouble, and they probably shouldn't even make them so people would have to buy and install a new cable, which is what the real solution is. Any time you see those replacement clamps you can bet you're gonna end up buying a new OEM type cable and you'd be better off doing that first instead of last.
@@truthsmiles You really touched on 'it' there. Remember the door flying off the Boeing 737? The plane was taken off their 'over water' flight routes because of continued cabin pressure warnings. The aircraft was talking but no one was listening.
This saved me replacing a starter and battery on my boat which it really seemed like both were bad... by testing and not guessing it was obvious I was getting voltage drop on a corroded positive battery cable. the negative side was fine.
Voltage drop follows Kirchhoff's voltage law where the sum of all the voltages in a closed loop are equal to zero. In other words, the sum of all the voltage drops in a circuit is equal to source voltage. Preferably we want all the voltage drop to occur at the load and not at a bad connection.
The key is *current*... V = IR... volts equals amps times resistance. I.E. if you don't put a load you won't see a drop. Eric mentioned that at the end.
I hope some HVAC techs watch this! Over and over and over again I ask will your multimeter read minimum volts and stay locked on that reading until cleared. In 30 years I have had two that said yes. The complaints are compressor failures, compressor hard to start lights dimming when compressor starts. My favorite is we sold the customer a completely new system and it has the same issue. We are dealing with 240 VAC at maybe 100 amps starting current. They get a good meter and find that 240 VAC is dropping to 150 VAC bingo Yahtzee! Now it’s always I will have customer call an electrician. Why just do voltage drop tests all the way to the distribution panel buss bars. If it’s dropping at the buss bars it’s a power company issue. So let’s save the customer the electrician cost and direct customer in the correct directions. Multi meters without low voltage lock are like an amp probe without a display. Thank you Eric for showing the value of knowing and not guessing.
Thanks for the education Eric I became a pretty damn good troubleshooter from watching you from the early days before dollar store glasses for both of us. Your explanations of electrical troubleshooting wasen't lost on me Thanks from an OG
CHIA!!!! Why wouldn't there be chia in a battery terminal down there. Why can't they put the windshield washer fluid down there and put the battery up top like they did years ago? If my windshield fluid freezes up when it's 30 below zero...not so bad. When the battery freezes up and you've got to get it out of there in the middle of nowhere...pretty bad. Thanks Mr. O, I think I have a better idea of voltage drop after this video. Thanks again.
Thank you for this informative video, my 98 c5 died and this explained where to find my drop. New battery and different headlights no more voltage drop
Mr O, you are a FANTASTIC Teacher!!! I wish I knew how to do voltage drop testing when I was working as a mechanic It would have come in VERY handy!!! And you explain it clearly and concisely and in a way that’s easy to understand!! Thank you for sharing your expertise with us!!
Sad part is, I think it cooked the battery a bit... This wasn't letting the battery fully charge that whole time.. and now the starter is dragging the battery down below 9v.. So it probably needs a new battery too.. soon.
To go through that much of a PITA to replace a Battery and a Starter....... Why would you NOT Clean all of the Connection Points?? Wonder what the Starter connections Look Like???? Learned something new today.
Nothing like a professional who knows what he is doing. Based on the equipment Eric uses, I spent the money on a used meter like his. It has kept me out of trouble several times. Thanks for the great video.
How much of the voltage drop was added by using the steel screw driver? I know it has a low gauge, but it is steel, which has more resistance than copper or aluminum. Not questioning the diagnostics at all, but I was expecting you put the resistance of the screw driver in your calculations. Been watching you now for years, so I'm so proud of myself for even posing the question, so don't flame me, as this is the best day of my life. BZ
Great tutorial. Now the question becomes: Does the other shop eat the starter and the battery and Eric O's diagnosis charge? I know Eric O. would - although he wouldn't have missed the diagnosis and perform the subsequent unecessary repair in the first place. Battery + starter + labor on that job gotta be $500.
I started learning electronics in the 50's by going on service calls with my dad to fix people's TVs. Yes, TVs were once repairable in the home, usually by replacing a vacuum tube or 2. There were no circuit boards; all the connections were point to point wiring. Any bad soldering joint could cause problems. When I started repairing electronics, I learned that most of the "unsolvable" problems were caused by bad ground connections. The higher the circuit current was, the bigger the voltage drop.
At 4:19 and 6:07 To stop the disagreers, Instead of removing the black negative lead from the screwdriver shank and then clipping it onto the ground stud, leave the black lead on the screwdriver shank and pull the whole screwdriver up and probe the ground stud with the tip of the screwdriver to show that using the screwdriver as an extension probe doesn't change the readings or add any more voltage drop. It probably won't shut up or stop the disagreers from disagreeing all the time, but that's because those people are just naturally disagreeable.
That could be the first time I've ever seen Luna's cry for attention get ignored. I'm sure she got extra ear scratches after the camera was turned off. Thanks for the videos, Mr O.
I always like your electrical and voltage drop videos, using the long screw driver to get to a hard spot, I never would have thought of that. Don't ever think we get tired of them, we don't, we always learn something.
So the new starter for the customer is just a bonus? Shops must feel pretty confident in Avoca, knowing if they can't fix it they can just send it to you. 😂
I’m pretty shocked and disappointed that the previous shop went to all the trouble install a new battery never bothered to clean the old terminals. that’s one of the first things you’re taught to do when you learn to change your battery. I wonder if that Honda requires the battery to be registered and if they did it properly
Eric, I just fixed and issue on my boat, by knowing how to check for voltage drop from watching your other videos, this one is great for learning, keep it up.
I really learn a lot from watching your videos and you never let me down. Always interesting and informative. The only thing that would make it over the top would be a cameo of Mrs. O 😂 Great channel!
Retired electrical engineer. Your explanation is spot on. Ohms law says it takes 1 volt to push 1 amp through 1 ohm. Every connection, piece of wire and anything else between two points is potential resistance. The rusty terminal caused the extra resistance in this circuit. The conservation of energy law says that energy cannot be destroyed, just transferred. With resistance, its's transferred to heat. As the temperature on that rusty terminal was raised, the resistance got worse and made the voltage drop worse until the point where there wasn't enough voltage to start the car. We saw this on the Honda battery terminal in your last video when you "let the smoke out". Again, spot on, perfectly explained and easily understood..... When your body gives out from working on cars, you should teach......🙂
👍
He teaches with every video he posts!
Fully agreed! I, too gave up mechanics to teach at a mechanic's school. Did it for 18 yrs. Let me clarify Ohm's Law: Volts= Amps X Resistance. So, 2 volts will not push 2 amps of current thru 2 ohms resistance. Electricity is so easy, once you know and fully understand how it works, but it is a total mystery if you don't understand it.
@@61rampy65lol Your both correct! 1 v = 1 amp x 1 ohm, and 2 v does not = 2 amps x 2 ohms. 😮😂
@@61rampy65 Electricity is easy in DC... things get a little bit more complex in AC. Luckily not an issue in the car world.
It’s always fun to watch a pro at work.
I learned years ago clean everything like you are going to serve thanksgiving dinner on it like Bill Hewitt used to say. It doesn’t take much to reduce the pixies from flowing correctly.
Great video
I hope they put back the old battery and starter, nope just didn't tell the customer the real problem. I'd say you need to run classes to teach the techs around you but that would kill a revenue stream 😅
Here's to hopping!!
Totally doubt it.
so, previous shop/s did the old parts cannon, including "a battery" and weren't bright enough to clean the terminals or see that was an issue visually? ay caramba!
I tried that test... I placed the screwdriver end on battery positive. Why did my screwdriver get red hot & partially melt? I gave it a good 45 seconds to see if it would stop. It didn't! Very difficult to remove the screwdriver, as it appears to have melted onto the positive post... Should I replace the battery now?
This is exactly why my headlights were flickering on my 2011 Silverado. Bad negative terminal at the battery. After a round of UA-cam voltage drop lessons, I narrowed it down and replaced the terminal end. Fixed the problem, and gave myself confidence that “If you can do it, I can do it.”
@@chuy1674 The battery terminal ends on those trucks are enclosed so you can’t even see the green puss taking over the cable inside. I couldn’t see it until I cut the cable off. But I figured it out with a multimeter and SMA lessons.
I had a voltage drop from battery hitting radiator and loosing the acid. Lots of soldering to repair the wire harness under the radiator. Used a lot of baking soda as well.
Well done .
An old man's car died in the McDonald's drive-through. After pushing him out of the lane I figured out that it was getting no fuel. I diagnosed a dead fuel pump, and he said that was his third dead fuel pump in 18 months. But I also noticed on the computer that the car was showing only 10 volts when running. I replaced the fuel pump and his car ran again, but I also knew that the low voltage could be the reason the fuel pumps were dying. The very first thing I checked for voltage drop was from the battery post to the battery clamp, and there were my 4 volts, basically two volts per post. I removed the clamps and found both posts coated with something like varnish. I cleaned them and boom, 14 volts when the engine was running. Hopefully that will keep the new fuel pump from burning out fast like the previous ones. By the way, I'm a DIYer who learned voltage drop testing on this channel (along with most of everything else I know about cars).
that's called low voltage burnout. as the voltage decreases, current consumed increases causing premature wear. also why it is not recommended to keep cranking the starter when the battery is low. if you ever see a car keep blowing bulbs there could also be a similar issue. great job helping the old dude out!
Awesome!!! 👍
Ive made thousands of dollars using simple good techniques i picked up from watching sma
@@user-fw8kt9dq9m I think that only applies to motors or possibly solenoids but on a bulb circuit it's simple V= IR there's no back EMF or whatever
Me too I learned a lot from this guy
Can't believe whoever went through the hassle to change that battery didn't take 2 minutes to clean visible rust/ corrosion off the clamp and cable. Also can't believe anybody else does a better job of explaining electrical diagnosis and trouble shooting than you do. Thanks and keep it up!
A hack. There are so many out there. It’s scary.
agree 100%
Guess who pays for a new battery that they did not even need?!!
Why get paid once when you can get paid twice!
It was completely accessible while the headlight was off.
You always are methodical and use logic which is why we are all here, to see a master at his craft.
Amen
Eric has a better understanding of electrical diagnosis than many electricians I have worked with.
Being an electrician is about knowing code not electricity.
most electricians don't know much electrical theory
I repair radiation treatment systems for a living and this is a very good refresher for anyone. You did an outstanding job on this.
The video makes perfect sense, but the fact that they had the battery replaced to attempt to fix this problem without cleaning the terminals is crazy! Great job once again Eric!
Parts cannon strikes again!
I learned voltage drop when I was in trade school. That was a long time ago. (1984), Over the past 40 years I've only had a handful of times when it would have come in handy, but of course, for the most part I worked at new car dealerships. I'm semi retired now and I work on old rusty junk. These refresher courses on voltage drop will come in handy. Thank you.
New car dealerships typically see cars that are less than 5 years old. The built-up resistance usually follows after more years have passed. Independent shops see them all the time because they work on a range of old & new cars.
Wow 1984....a long time ago...me too, us old school mechanics ....Yes the video was a good refresher....
Gotta love Dodge aka Stellantis for putting the battery in such a remarkably accessible position, aye? Thanks for the educational video, Eric!
nissan does it too.
@@sockmonkey3393both junk brands!
A most eloquent and thorough articulation of voltage drop consequences and testing. Well done, as always, Eric. Best wishes for continued success from Florida.
Where’s Mrs. O? Always fun to watch you cower in her presence. 😂😂
I really like this channel. 1 - you cover the essentials of being a mechanic in the rust belt. 2 - you cover what is involved in diagnosing and fixing modern cars. As you said once, it is all about the data. Thankyou Mr O and Mrs O.
The wire whisperer strikes again!!!
One the days when I am feeling old, I point the FLIR camera at it after cranking the engine, and look for the hot spots. The voltage drop check is still more accurate and cheaper, though. I bought the silly thing to test cooling systems and catalytic converters, but ended up using it for electrical faults. Hotspot in a fuse box? Boom. Found it. At least it wasn't a total waste of money.
You make the testing process so simple, but I find myself disturbed by the fact that the "other shop" was unable/unwilling/not smart enough to do such a simple test. Instead they fired off the parts cannon for hundreds of (perhaps unnecessary) dollars. Then they send the car to you, you identify the issue, and they finally fix the actual problem and the customer ends up being oblivious to the fact that they've been ripped off due to that shop's incompetence/laziness/greed.
I think that junkyard paint on the light is telling a story. Perhaps one like that's how the body shop put it back together after it got hit in the front end.
I would like to double-like this comment ;-)
It is funny just how much I learn from every video that you put out. Keep them coming.
Eric, a great tutorial. One of the additional challenges of looking for the trouble spot is finding a way to probe a connection point and the connected conductor. Over the years my collection of DVM probes with weapon sharp edges and a variety of file sharpened back probes has filled a shoe box. Surface oxidation of a connector or exposed conductor can be an additional challenge. BTW the insulation piercing adjustable needle probes made by Pomona are wonderful. I always seal the pin holes in wire insulation with liquid electrical tape afterwards. As you aptly pointed out ,every mechanical interface in a circuit is a potential failure point . Be thankful you don’t have a boat that is used in a salt water environment. Every connection point is a potential trouble spot. It’s beginning to look like this is the reason why the electrical system in the MV Dali container ship failed at a most inappropriate time. Dude, you are a wonderful instructor . With all the electronics in cars these days , an individual with a good basic understanding of electronics and electricity will be a superior automotive diagnostic tech.
Awsome!! 2 new videos in the same day!! Thanks!! Keep up the awesome job!!
Great demonstration! I typically teach a maximum of 0.1v per connection and 0.1v for every meter of battery cable. Never to exceed 0.5v for the entire insulated circuit or entire ground circuit..This only applies to high current circuits such as starter and alternator testing. I'll bet on that car if you cranked it for 15 seconds in clear flood mode you would be able to "see" a hot connection with a thermal camera. 1volt times 100amps is 100watts. That's got to warm up something...
Smoke is always a good visual que ;-)
@@SouthMainAuto visual cue
In aviation, a 0.5V drop applies to any circuit carrying power not just the big ones. The tables in AC 43.13-1b go down to at least 22AWG. They also differentiate between continuous and intermittent loads. They allow a 1V drop for intermittent loads.
@@major__kong that's interesting
disable fuel/spark and crank until something emits smoke.... 🤪 even if manually via starter relay jumping. wait I would never do such a thing and have never( yeah right, look for smoke first, then troubleshoot second)
12:02 Kitty sighting. Appears to have been underneath the car checking connections for rodents.
Or asleep.
Luna was doing a cat scan.
@@glassvial and kitty head shake--that must be the "negative" sign for scan results.
So easy but people get it so wrong... I will never understand! But I guess that is what really sets shops like yours apart. "Knowing your craft".
Curious what the resistance was between the battery post and terminal.
Eric, you are lucky. You are constantly receiving cars where ALL the swapnostics have already been done, allowing you to focus on the real problem😁
Ha!
I learned the hard way too that checking every connection point also applies when checking for opens/shorts. I couldn't figure out why one of my TPS on the throttle body was showing 0v but everywhere in the circuit was 5v. Then by accident I pressed really hard on the connecter and the voltage came back, some how there was a failure from the back of the wire in the connector to the front of the pin, lol. I checked the voltage everywhere except the place it mattered, lol.
Voltage Drop - a classic reggae song - voltage gonna drop on you...
You speak pretty good jibber jabber! I understood it perfectly. Thanks Mr O.
Saturday with Mr. O is better than Saturday cartoons. You can learn so much from this UA-cam Channel.
HE IS THE BEST.
Very informational video like most that you put on "the UA-cams". Keep up the great work
I'm a bad mechanic but have used this technique many times. I don't understand how the prior shop just decided to fire the parts cannon at this problem. What the hell?
Great basic troubleshooting techniques. So many take their best guess and fire the parts cannon.
South Main Auto... Very well explained Eric. As always my friend.
Several years ago my wife bought a Chrysler Pacifica at another state car lot. (When Pacifica was an Suv type vehicle). It was low mileage great condition, optioned out and a great price. We picked it up on vacation on the way home. About 150 miles on the 250 miles trip the dash went dead and engine turned off. A call to the dealer who denied any knowledge advised to take it to a dealership. It was late afternoon Saturday so nothing open. I made it the rest of the way with no more issues. Now thinking I'd been scammed (deal too good to be true). I simply Googled the model and symptom and then answer was a bad connector on the hot cable from the battery connector to the fuse module. Monday I called the local deal to get a replacement. Of course back ordered with no known date. I measured the diameter and length of the cable, went to tsc and picked up a riding lawnmower starter cable that was the same diameter but 1 inch longer. I swapped the cables and she drove it for the next year and we sold it. We made a little over $4000 on that vehicle by replacing a $3.95 cable.
Yea TSC!
Ain't it funny how weird issues always seem to affect components that are installed in dumb places....
Thxs Eric some good info....You showed us in lasted video the cable exchange....Thxs again...
Eric, you are so right when you say that everything imposes a bit of voltage drop. One item that has to do this is the fuse. It relies on having a certain resistance so that when the current gets abnormally large the wire in the fuse will heat up and eventually melt. You often see a largish fuse (e.g. 15A) protecting a circuit taking (normally) only a few tens of milliamps. The fuse size is chosen to protect the wiring and also ensure that normal voltage drop across it is small so as not to affect operation.
I learned that lesson from one of Eric's videos.
For you auto restoration folks with 6 volt systems ( more common than you know ). The 6 volt systems are super sensitive to any corrosion. Internal corrosion INSIDE cables OR use of much lighter gauge ( 12 volt rated cables) will cause starting problems. Remember the GROUND SIDE of the circuit needs clean connection. CLEAN. ALSO as heat is generated by high current voltage drops you can quickly touch the cables and besides giving yourself a first degree burn can isolate the source of the voltage drop.
Thank you for all the knowledge my friend. You have a simple yet informative way of explaining that makes it easy to understand.
Just watched Paul’s video and then yours popped up.
Have a great Saturday.
A very good lesson. Thanks, Eric.
the problerm is usually in the most inaccessible location....!
Disconnecting and cleaning all ground connections would be the thing to do if we don't know how to troubleshoot using voltage drops. Having the scope is perfect because we capture the voltage level when doing something like turning the ignition switch etc. Much nicer than using a VOM. The next best thing would be using a VOM that records min and max voltage levels.
Aftermarket systems installed on vehicles can cause a LOT of voltage drop problems in fleet vehicles. Then they became our problems when they didn't work right.
Or when a three axle tractor with trailer had a problem with the OEM instrumentation not reading correctly and for several months the problem was chased.
When the vehicle came in one day the dash voltmeter read in the 11 volt range. With the engine running, one of the two group 31S batteries read 14.2 volts the other read 12.4. Both batteries had individual positive and negative cables going to the starter. When the cables were checked by pulling on the cables near the lugs (terminal) at the starter one cable pulled out of its lug.
It took a little work to fix it but once repaired both batteries read 13.5 volts, no more voltage drop and that repair eliminated all the electrical problems in the vehicle's instrumentation. YA. VOLTAGE DROPS ! !
Good one Mr. O!
When you have a problem like this and you got an old car the best thing to do is just go ahead and change the positive and the negative cables that will eliminate your issues and your your battery will hold the charge and it's a cheap fix especially if you do it yourself
Dude you didn't even say hi to Luna. Rude..
lol, i was waiting for that too.
Didn’t know you had a catwalk in the shop Eric. Saw Luna there strutting there like a queen she thinks she is. 🤣
I worked in electronics for many years do bench repair of PC boards and used this troubleshooting method all the time. Worked with many techs that would shotgun and sometimes finally got a fix.
This is how i fixed my son's car. Battery kept going dead. I knew it was a draw from some where. Watch a few of your other videos on voltage drop, current draw, etc. Knowing what circuits had full time power was a big help. Found the draw. What able to isolate the components. Found the problem. Thanks you for your help and breaking it down Barney style.
Glad to help 😊
Thanks for a good explanation 😊
Glad it was helpful!
@@SouthMainAuto Nah, wasn't any help because I don't have any of those problems because I learned years ago that those aftermarket replacement battery post and cable clamps are crap and nothing but trouble, and they probably shouldn't even make them so people would have to buy and install a new cable, which is what the real solution is. Any time you see those replacement clamps you can bet you're gonna end up buying a new OEM type cable and you'd be better off doing that first instead of last.
Great refresher course. People always want the "fast fix" and need to realize the importance of voltage drop testing.
The irony is this IS the “fast fix” - this car has been giving problems for days if not weeks and Eric found the problem inside of an hour.
@@truthsmiles You really touched on 'it' there. Remember the door flying off the Boeing 737?
The plane was taken off their 'over water' flight routes because of continued cabin pressure warnings.
The aircraft was talking but no one was listening.
This saved me replacing a starter and battery on my boat which it really seemed like both were bad... by testing and not guessing it was obvious I was getting voltage drop on a corroded positive battery cable. the negative side was fine.
Voltage drop follows Kirchhoff's voltage law where the sum of all the voltages in a closed loop are equal to zero. In other words, the sum of all the voltage drops in a circuit is equal to source voltage. Preferably we want all the voltage drop to occur at the load and not at a bad connection.
The key is *current*... V = IR... volts equals amps times resistance. I.E. if you don't put a load you won't see a drop. Eric mentioned that at the end.
I hope some HVAC techs watch this! Over and over and over again I ask will your multimeter read minimum volts and stay locked on that reading until cleared. In 30 years I have had two that said yes. The complaints are compressor failures, compressor hard to start lights dimming when compressor starts. My favorite is we sold the customer a completely new system and it has the same issue. We are dealing with 240 VAC at maybe 100 amps starting current. They get a good meter and find that 240 VAC is dropping to 150 VAC bingo Yahtzee! Now it’s always I will have customer call an electrician. Why just do voltage drop tests all the way to the distribution panel buss bars. If it’s dropping at the buss bars it’s a power company issue. So let’s save the customer the electrician cost and direct customer in the correct directions. Multi meters without low voltage lock are like an amp probe without a display. Thank you Eric for showing the value of knowing and not guessing.
A Chrysler quality product with a bad ground?
Imagine my shock!
with all voltage drop testing THE CIRCUIT MUST BE UNDER A LOAD!!!!!. If not figure a way to load it.
Thanks for the education Eric I became a pretty damn good troubleshooter from watching you from the early days before dollar store glasses for both of us. Your explanations of electrical troubleshooting wasen't lost on me
Thanks from an OG
CHIA!!!! Why wouldn't there be chia in a battery terminal down there. Why can't they put the windshield washer fluid down there and put the battery up top like they did years ago? If my windshield fluid freezes up when it's 30 below zero...not so bad. When the battery freezes up and you've got to get it out of there in the middle of nowhere...pretty bad. Thanks Mr. O, I think I have a better idea of voltage drop after this video. Thanks again.
I live in the North woods you must clean your battery connections every six months !!! I use brass boat battery clamps they are better !
Thank you for this informative video, my 98 c5 died and this explained where to find my drop. New battery and different headlights no more voltage drop
Excellent walk-thru and very useful. Thanks for this!
You explain things very well and I have learned a great deal by watching your videos.
Keep em coming!
I’d love if we could test people for voltage drop. 😂
Like Trump.
@@kiwiingenuity1677he may have a voltage drop but his battery isn't completely dry like Mr where am I!!!
Mr O, you are a FANTASTIC Teacher!!! I wish I knew how to do voltage drop testing when I was working as a mechanic It would have come in VERY handy!!!
And you explain it clearly and concisely and in a way that’s easy to understand!!
Thank you for sharing your expertise with us!!
Eric gets us to the answers by the shortest possible route. Love it!
Sad part is, I think it cooked the battery a bit... This wasn't letting the battery fully charge that whole time.. and now the starter is dragging the battery down below 9v.. So it probably needs a new battery too.. soon.
Agreed. If the battery was left overnight below 12V its lifespan would be reduced. Depends how much it was driven by the owner.
To go through that much of a PITA to replace a Battery and a Starter....... Why would you NOT Clean all of the Connection Points?? Wonder what the Starter connections Look Like???? Learned something new today.
Great video. I know it added a lot of time to this diagnosis so thank you for sharing.
Thanks for the....explain. Learned much, as I always do the way you explain things. Thank You Mr O. So simple!!!
Nothing like a professional who knows what he is doing. Based on the equipment Eric uses, I spent the money on a used meter like his. It has kept me out of trouble several times. Thanks for the great video.
How much of the voltage drop was added by using the steel screw driver? I know it has a low gauge, but it is steel, which has more resistance than copper or aluminum. Not questioning the diagnostics at all, but I was expecting you put the resistance of the screw driver in your calculations. Been watching you now for years, so I'm so proud of myself for even posing the question, so don't flame me, as this is the best day of my life. BZ
You really need to start charging a "you had it at the unconfident shop first" fee of $300.00 min.
PS the cat so bombed your video; it knows what it is doing.
Great tutorial. Now the question becomes: Does the other shop eat the starter and the battery and Eric O's diagnosis charge? I know Eric O. would - although he wouldn't have missed the diagnosis and perform the subsequent unecessary repair in the first place. Battery + starter + labor on that job gotta be $500.
Thanks, I learned something today. I was going to ask about measuring OHMs but you answered my question.
I started learning electronics in the 50's by going on service calls with my dad to fix people's TVs. Yes, TVs were once repairable in the home, usually by replacing a vacuum tube or 2. There were no circuit boards; all the connections were point to point wiring. Any bad soldering joint could cause problems. When I started repairing electronics, I learned that most of the "unsolvable" problems were caused by bad ground connections. The higher the circuit current was, the bigger the voltage drop.
Perfect!! 👍🏼
It’s crazy how that connection is robbing 1 Volt just bc it’s cruddy.🤯
At 4:19 and 6:07 To stop the disagreers, Instead of removing the black negative lead from the screwdriver shank and then clipping it onto the ground stud, leave the black lead on the screwdriver shank and pull the whole screwdriver up and probe the ground stud with the tip of the screwdriver to show that using the screwdriver as an extension probe doesn't change the readings or add any more voltage drop. It probably won't shut up or stop the disagreers from disagreeing all the time, but that's because those people are just naturally disagreeable.
Confirmed @12.01 by a CAT scam !
The customer should have Brought it to you first .would have saved him some money .
Nicely explained 👌
That could be the first time I've ever seen Luna's cry for attention get ignored. I'm sure she got extra ear scratches after the camera was turned off. Thanks for the videos, Mr O.
I always like your electrical and voltage drop videos, using the long screw driver to get to a hard spot, I never would have thought of that. Don't ever think we get tired of them, we don't, we always learn something.
So the new starter for the customer is just a bonus?
Shops must feel pretty confident in Avoca, knowing if they can't fix it they can just send it to you.
😂
I saw your portable cat scan machine walk by. Informative video and thanks for the instruction.
This and the two Honda videos are invaluable ( by which I mean there is no way to give it a greater value)
You have to Wonder who the Designers were of the Dodge, Chrysler and Plymouth Models over the Years. Stellantis is in Huge Financial Trouble. R.I.P. 🙏
I’m pretty shocked and disappointed that the previous shop went to all the trouble install a new battery never bothered to clean the old terminals. that’s one of the first things you’re taught to do when you learn to change your battery. I wonder if that Honda requires the battery to be registered and if they did it properly
🤷♂️
Great Saturday morning coffee video, love all the electrical vids Eric. Have a great weekend 👍
That makes sense AND makes cents 💰 in saving us money with your techniques ! Thanks Eric .
👊🏼 🔥 💻 📈 💡
A Master class! I am thankful you do not charge what your classes are worth! Thank you so much!
Eric, I just fixed and issue on my boat, by knowing how to check for voltage drop from watching your other videos, this one is great for learning, keep it up.
I really learn a lot from watching your videos and you never let me down. Always interesting and informative. The only thing that would make it over the top would be a cameo of Mrs. O 😂
Great channel!
Thanks Eric. Your explanations are so clear, if a viewer doesnt understand voltage drop after this, they should perhaps reconsider their interrests.:D
I always remember - “all of the voltage is used to overcome the resistance of the circuit, the only real resistance should be the load item itself”