NEWS FLASH!! Ohmmeters will lie to you! Between flow charts written with an ohmmeter as the tool of choice and then people telling me "you should have measured resistance on that circuit, you are over-complicating things with your methods", I've seriously had enough! Time for everyone to learn something. Watch close and never tell me again to use an ohmmeter in a case like this. Here is the original video on UA-cam Poor running, flashing CEL, no codes (bad computer ground) - Toyota ua-cam.com/video/44dP6X3QS5A/v-deo.html Here is the SD Premium video I am recommending as a follow up www.scannerdanner.com/scannerdanner-premium-chapters/basic-electrical-concepts/485-basic-electrical-review-part-2.html
What I learned from u is good continuity does not mean good CONDUCTIVITY Check voltage drop of the circuit current has to flow A continuity test can’t verify the ability to handle the circuit current
Hi Paul! I’m an EE and I’m not surprised at all that another EE would say that. I worked with several EEs who came out of school and although they knew the academics, they weren’t worth a crap in the field troubleshooting automated industrial equipment. I can remember asking one “How should we test this cable?” This cable was for a 250 amp DC power supply. You guessed it as an ohmmeter was his answer. Then I had to teach him about voltage drop testing which of course he never heard of. 👍
freaking awesome, voltage drop for the win !!!!! Paul how dare they try to question your skills ??? good thing you showed them !!!!! hey buddy sign up for scannerdanner premium maybe you'll learn a thing or two lol !!!!!Paul for president 2020 !!!!!
If engineers had to fix the garbage they design today, things would get MUCH easier for us in the shop, that's for damn sure. GREAT explanation as always, Paul. Great to see Caleb absorbing all this knowledge, too. He's probably already a better diagnostic tech than I, and I've been doing this as long as I can remember. 😎
I teach for a major auto manufacturer and we teach voltage drop. We even show where the resistance check will lie to you. It's all about the voltage drop or load testing.
Archie I took 2 of your electrical classes back in 2017 or 2018 and I remember you telling the class this. To this day your classes were some of the best training I've ever had
He did and to be fair he was not being a d-ick in anyway. It just struck a nerve for me because he quoted exactly what a manufacturer flow chart would have you do.
Thank you thank you. Techs have to fix all bad engineering. Work for international dealer boy if the public can only see what they build. You would run the other way.
I agree some.u gotta think engineers cant think of every aspect of wat they design.its so many things that have to be factored in.do they say i wonder if i put this in this location would it be easy for the tech to repair.no.thats the reason why they r constantly changing things.its easy to blame them.those guys r brilliant.2 thats why they make more than us.
I have proven to myself that the load pro works great for such occasions. Not advertising here but the darn thing works on my meter like a charm. I myself have used the ohm meter and misdiagnosed a simple problem. Spot on !!
I totally remember that Toyota video..Lol. Great lesson on why voltage drop is best. Thanks for sharing this Paul. Great video.! Put that freaking Ohmmeter BACK in the toolbox.! 😂😂👍🍻 Cheers Brotha
Totally agree. The other down side to Ohm checks is you have to isolate the circuit. Which means disconnecting stuff & ultimately changing the circuit. The Observer Effect at it's finest (the mere observation of a phenomenon inevitably changes that phenomenon). Sometimes simply touching the wires/connectors will 'fix' the problem, sending you down a rabbit hole and possibly never finding the problem. So if you can test the circuit with the circuit untouched, you will have a higher probability of success (and probably develop less gray hairs in the process).
Hi SD. I'm also an EE and I was thinking, you can't get the required resolution using a simple ohmmeter to tell a bad ground. As you said, 30A through .1 ohms will show 3V of drop and anyone looking at .1 ohms would probably call it good.. Not to mention, the ohmmeter won't heat up a connection like current flow will. Agreed, voltage drop all the way.
I agree with your assessment that the resolution of the ohms meter isn't good enough. Paul, I'd love to see an experiment next time you run into one of these. Measure current as well as voltage drop on the bad connection. We could use ohms law to prove that there is measurable resistance there, the meter just isn't good enough to report it.
Load Pro works, but it is not the "end all" tool. I have had cases with resistance the load pro didn't detect. Happened to me recently on a BMW with a loose ground cable.
GM teaches us how to do voltage drop, but really focuses on resistance measurements. I’ll do them on cars where I have no idea what’s going on and need to follow the flow chart (unfortunately) but your methods have really opened up my diagnostic abilities over the last year and I just wish I had more time to go through your stuff
That's awesome professor. It's a good feeling proving people wrong. I remember that case study u were talking about the 900 ohm of resistance on that GM vehicle with the aftermarket alarm system that the customer didn't even know was there. Great job professor. Cant wait for the navigator case study. Take care 😀
You teach what works best for you. The do it your selfers will have to make up their own minds. Just keep teaching mate. Knowledge is all we really have to keep. Your work is appreciated.
I'm a field tech for an OEM too and my side teaches DVOM circuit diag and voltage drop. However, our tech hotline doesn't push voltage drop testing or load testing as much as I would like. Hate it when I have to travel accross the country to find a lousy ground or power supply!
The EE's flow charts don't Stress, Load, or Strain the wires in question as you have by turning the key ON, and pressurizing the circuits to their normal capacity, to "catch" excessive drops in voltage with Ground- to-Ground voltage drop checks. I've heard it called 'stealing" voltage from the circuit, which in your case was the corrosion . I hope this makes your case stronger!!
Absolutely agree. Loaded voltage drop test is the way to prove wire integrity. In the electrical field the utility workers have what they call "the beast". They clamp on at the meter and seriously load the service drop. If there is a weak connection you will see a voltage drop. I might add, even on a short to ground or ground fault i tend to grab my megohm tester. A gfci trouble call can be hard to trace with a wimpy ohmmeter. Put 500 volts and ground fault shows up easy. (Not for cars) love engineers but sometimes......a little experience goes a long way! Cheers
@@ScannerDanner lol. It will tickle. A bit like the spark plug. It's actually referred to as an insulation tester. Commonly used to test motor windings. In nj, we had to megtest wiring that had not been permitted. If a nail or staple knicked a wire this would show. My fluke 1507 can test @ 50,100,250,500, and 1000 volts. I imagine on a car you could fry stuff if not careful. Same precaution as welding on a car? Cheers
@@ScannerDanner a insulation resistance (megger tester) is commonly used for testing insulation resistance on high voltage motor windings etc. It applys a large voltage to the circuit and measures the current flow to provide a resistance measurement. Unfortunately they don't suit testing low voltage systems.
@@ScannerDanner I've heard you say it in other videos but the ohm meter is testing at very low voltage/current. The closer the test matches real conditions the better. So, yeah you hit the nail on the head. I plan on buying a test light asap. (From your friends JB) like you, i love an excuse to buy a new tool! Honestly, half the reason i love your channel is seeing all the cool tools! Cheers
ScannerDanner. I thank you. Your theory on chequing the voltage drop. Am not an electrician. I don't know why people who are experienced electricians. Can see the easy practicality of your sureshot tecnique. But it sure will make second guessing. Away with the useless time wasted. You're right on the money. Ohms quantity testing - Like you said on the engine grounds going to the computer. It's a waste. Unless you take your time to inspect the conditions for a solid ground. Going to the computer 💪💪. Always checking voltage drops. I would say. On every electrical problem is 🔑👍. Making sure the relay is okay every time.
Using a test lead on your Power probe 4 . Go to Feed mode and touch those same points. The red or green Led will light up / annoying sound to let you know if you have a good ground or power etc...also you can read the resistance at the same time. It will not light up or sound off if there is high resistance. The PP4 will load the circuit internally like your test light. Great learning video 👍 you guys made
I agree with you 100%. Problem is that ohm testing is still being taught to apprentices here in New Zealand, and probably many countries. The use of an incandescent test light is not allowed here in many workshops because of the damage they cause!! Their reasoning is beyond belief. I'm sure some instructors & techs still think the world is flat!
I got "burned" a little using the DVM a few months ago fixing my horn circuit problem on the 1999 Silverado; the test light came to the rescue and proved I was chasing a ghost..
Current handling wire and connections with dissimilar metals & corrosion will get you over time; happens all the time with aging "stuff"; more so in the "salt belt" areas of the country.
fact I went to Nashville auto diesel 2001 15k I learned the material now I a danner premium guy fixing a lot from his teaching. like a car or truck comes in late I kind of know what direction to go the next day so I watch mr danner premium channel at night bam the car is usually fixed with what I learned in less than a hr billed out the door if you own a car or truck worth the 11.00 to know how it works trust me it is going to break down DO YOU KNOW WHY. DANNER MAY BE ABLE TO TEACH YOU. thks paul
Haven’t finished watching this, but great point Paul. Basically it‘s like testing resistor in circuit on the PCB board. You can have reading 20ohm of 10kohm resistor. Does it mean that resistor broken? Of course no, it just act as a conductor, therefore until there are current it wont resist anything. Voltage drops and injecting some current are crucial things during troubleshooting electrical/electronic components of the car.
I agree. I believe you should know ohm testing on a fundamental level but should master the voltage drop testing. The times I’ve mostly used ohm testing is if I think I have an intermittent break in the wiring and I would use the graphing meter on each end of the wires and start wiggling the harness.
No scanner scanner, can't afford to take my 2004 Mercury Grand Marques, in to put in new electric cooling fan. My fan quit working, surfing largest snowstorm, in 50 years. Was rocking car back in forth in driveway, till engine shut down. It got hot, pcm said shut her Down! Couple hours later, it started, but engine fan never ran again. 2003-2005 Panther platform cars, use exactly same setup. Have Checked all fuses, relays, and diodes, and plugged in new fan assembly, it does not work!! Please text or call.
Voltage Drop Testing is always the way to go. Dan Sullivan has been aware of this for many years. This is why he invented the LOADpro diagnostic tool. And this is why I bought one for myself. It's important to mention that you should always make sure that you have a fully charged battery and that all grounds are good and all your terminals and posts have been taken apart and cleaned and reinstalled. The same applies to the Battery Posts the Positive and Ground Cables as well looking for Corrosion and damaged cable insulation. The Voltage drop test will the level of Resistance in the circuit if any. Then you can investigate if the problem is on the Positive side or the ground side or is it simply a defective part that needs to be replaced. I am one of your loyal subscribers. 👍👍
0:51 not to make fun of the engineer or all engineers in general, i(FNG as a dealer tech) had a 15 sienna come in for a no-a/c complaint, found out it has a code for the clutch lock-up circuit(essentially something that sends the signal to the computer to request a/c operation) well this vehicle had a new clutch-coil put on at the previous toyota dealer(out of state, why they put a clutch-coil on i dont know but thats what they did) but its still not working, fixed the pin fitment issue that it had in the circuit but it still didnt work, so now i(the FNG) took out my ohm meter and said well the coil has 200ohms(it was right in the middle of spec) of resistance so it must be good, take a closer look and you will notice the wires were not routed correctly so now did i just measure the resistance of my pulley? new clutch coil and it works now, ENGINEERS! WE LIVE IN THE REAL WORLD! resistence measurement is not always the way to go, i personally try to use a test light(kinda like what SMA made in a video) but ill use the peanut bulb for circuit integrity to check my wires, im sure i will get a lot of hate for this comment edit: curious how bright/dim the test light would have been in that computer ground before the fix, thanks again for the great content!!
Glad you taught that electrical engineer something valuable for free that he didn't learn in college. Keep up the great work and proven information doesn't lie. :)
there is a proper meter that tests circuit "resistance" while under load ;) but I have a feeling that fella doesn't know what one is, perhaps he slept through his engineering (brainwash) degree and didn't bother to learn anything but :)) put heavy load on wire/s with test light/motor/load bank/etc. measure voltage drop point A to B, calculate the resistance from current, voltage/voltage drop.... yeah it;s best to have it on a stable current controlled supply and load bank. isn't that like engineering 101?
Since this is the latest video, I hope Mr. Danner gets to see this question which is perhaps more of an opinion. Furthermore, I hope he forgives the long post. My second profession before I retired had been working as an electrical contractor. Mainly in residential and office building market. The electrical system in a residential unit consists of three wires that come to the top of the house electrical panel and a GROUND wire that usually comes out of the bottom of the panel. This heavy wire connects to the house cold water pipes that are buried in the street (ground) and usually an eight (8) foot solid copper rod that is driven into ground. Called ground rod. Basically, the purpose of the ground system is to protect an occupant should a live wire touches the body of an appliance. The ground wire in an outlet or appliance, routes the live voltage to “ground” rather than the body of an occupant. Thus, preventing a heart attack. Now the reason for this post---I know I am probably going against many years of automotive electrical charts and training books, so bear with me. Why a body of an automobile is called “ground”? There is no connection between the vehicles body and the earth. Rubber tires prevent an electrical connection. In a simplified DC circuit; in order for any circuit to work, it requires a path for 12V positive to reach the load. It also needs a path of return to 12V negative, which are the two terminals on the battery. The automotive engineers figured that since there is metal in the frame and body of the powertrain, it would save wire (money) to use the frame as the path for negative voltage to battery. That is a great idea, but why call it “ground”? Why not call it chassis? After all the negative wire of the battery is connected to the chassis of an automobile. Anything, but “ground” makes more sense in a DC system.
The health of a circuit can only be determined when it's capable of flowing the designed current at the designed voltage. Makes total sense really. No one builds a circuit for the end-result of a resistance specification. The whole purpose of a circuit is to carry a specified current at a specified voltage.
I am a retired mechanic of 36 years on the job. I started working on cars in 1980 the first year GM had computers in cars. I did a lot of electrical work and in the early years i was factory trained. I always checked a ground with a ohm meter. You teach me something in almost all of your videos, I wish there were more teachers like you when i was starting. Anyone going into this field of work should at least subscribe to your premium channel i would have went to your classes!!!!! Thank you so much for being you, you are the best teacher anyone could ask for.
Would using the battery negative terminal and ohm meter or voltage drop both get the same result? Was the body ground vs the battery as a test point the issue? Thank you for all you do. BTW Genuine question just want to learn.
The glob of corrosion at the terminal has a non linear resistance. That is, the resistance changes depending on the current going through it not like a piece of copper wire which has the same resistance as the current changes. That's why your meter has a diode check setting to check diodes because diodes and semiconductors have a non linear resistance curve. Most people don't realize it but the reading in diode check is actually the voltage drop across the diode. Hum. I wonder what reading you would have gotten if you were to measure your bad ground with your meter set on diode check? If the ground was good it should read zero. Meters really don't mean to lie. They can only tell you what they can see.
you guys are the best. now on with the show ❤️️ much easier to do a voltage drop test or computer ground test and leave the ohmmeter locked up. Thanks, Paul and Caleb
What do you do on a car that randomly stalls? Dealer had had it for 2 weeks, no stall. I will take it home and 2 or 3 days later it will stall. Usually happens on a very hot day with a/c on. Never has a fault code.
I would turn the job down lol. But seriously, you would need test equipment hooked up and make it your everyday car with a list of checks to do for each stall and wait 3 days for the next one? See what I mean? No thanks. Need to break it more first then bring it to me. I can't drive customers cars around like that.
@@ScannerDanner in other words, sell the damn thing (i would tell the prospective new owner it has that issue). Thanks. I really do understand. Sad thing, it is a 2005 trailblazer with 50k miles and looks and drives (when it does) like a new car. Oh well, sometimes a low mileage car is worse than a high mileage one. Love your channel.
Start doing some common failure searches, this can narrow down the area of where to start testing, then get it to do it more often. Do the tests yourself and use my forum. It's free to join. Start with a throttle body cleaning and relearn then go from there.
A bad ground is like a kinked garden hose, an ohm meter is still going to show 0 ohms and voltage on a bad ground. Put a load on the bad ground and you will see the like kinked water hose, when the voltage is not there like the supplied voltage. nice video Mr Danner.
I'm also an engineer and I say use an ohm meter Danner cause does what my tech manual says!!!ohh and I confirmed that with my poodle and she suggested the same thing.
Garbage in Garbage out!.. load test/voltage drop test all power supplies. Fantastic video. The engineers are the ones that make these awful misleading flow charts.
I tell people load the circuit do your volt drops see what the real problem is. Everyone pushes off diag work to me that always seems like easy fixes like that !
GREAT INFO PAUL! I absolutely love love love the premium channel can't get enough of it you have taught me lots of valuable knowledge even for me being a heavy duty Diesel technician , It doesn't matter I work on literally everything. Appreciate all the hard work you put in these videos 👍🏼
This comment is awesome, thank you! Would you be willing to put this on my feedback page? Either way, it is so cool to hear how the material transcends the auto field (if that's the right wordl
I fail to see why you need a voltage drop test, when your ohmmeter showed a problem at the 7:20 mark. At the 7:20 mark, when 0.00 was read - that number right there indicated a problem. If you check the multimeter specs, for example, a Fluke 117 will not display a resistance above 0.00, until that resistance hits 0.1 ohms. When a meter reads 0.00, this indicates a resistance so low that it's lower than the meters resolution, but it does not indicate "0 resistance" as was assumed. There's no need to continue on with a voltage drop test. That 0.0 right there tells you it's a problem.
I was testing a GM air conditioner system on an S10. I had power everywhere it was supposed to be, had ground too. Circuit still failed to operate when i plugged everything back in. I switched to a test light and checked my meter, power, when i touched test light it dropped to "0". All became clear, LOAD THE CIRCUIT!! It was a bad relay, burned contacts the post mortem revealed. So i am absolutely on board. I have also discovered that electrical engineers generally go by the mantra "looks good on paper", as we know, in reality outside the draft board, its all very different.
Watching every single video of yours. Wish i could have seen all your videos when you started your career. Absolutely awesome videos. Calib you are blessed to be part of your dads business. First hand info. Absolutely brilliant. Thank you very much. I am not a mechanic but do work on peoples cars. Absolutely brilliant. Luv everything. Cannot get enough of your info. You are helping so many people. Watching your video, then go to my toyota to do same tests where possible. 👏👏👏👏
With this attitude, you will succeed! Watch all the free ones here on UA-cam, then come to my website if you want more. I have about 450 more video there with half of them classroom lectures where I invite you to be part of it online. www.scannerdanner.com/join-scannerdanner-premium.html
Fantastic vid. I was working on a No Crank No Start on a Bobcat. I was convinced it was somewhere in the ignition wiring. My test light bulb was burned out and I had no spares. At the time, I didn't have a power probe. So I used my multimeter and checked the resistances instead of repairing my tool kit... shame on me. I wasted unneeded time. I eventually pulled my head from my butt and borrowed my friend's test light. I started my tests and checks all over again. I followed the voltage drop test all the way to a hidden damaged wire within a very inconvenient place in the frame that was being held together by a single strand of wire. That single strand was enough to positively test continuity but would drop the voltage.
You did not used a regular multimeter to measure the voltage drop, you used a scope multimeter on a high resolutin scale. I did nt see a voltage measure with the yellow meter you measured resistence. With scope multimeter the voltage drop, varies very much in time (50 milisec), and the amplitude goes from -2 to 8 V so fast that the normal meter on DC scale will never show. Maybe a True RMS on AC would show someting. So, if we do not have a scope meter or a True RMS meter, what can we do ? Nice demonstration , thank you :)
The average of that signal was showing on the screen too. There was a min, max, and current digital reading. It would have definitely shown on a regular digital voltmeter. But good point about averages and some things can be missed. Not this one though. Thanks!
Why not both? I mean it ain't hard with a meter to just swap between the two and turn the car on and off. I feel like that would be a good way to just make sure you catch everything but good to know if I can only do one volt drop
For sure, you need the ohmmeter at times. In particular with CAN network disgnostics. But why is it good there? Because those are basically non current carrying circuits. So anything that has measurable current flow, the ohmmeter can test good but still be bad.
Many good points here and I'll make a point too. Comparing a low cost/accuracy multimeter to a high cost/accuracy scanner/oscilloscope isn't fair. And I'm with you on volt drop testing too.
it wasn't about a low cost meter. You could have used a fluke ohmmeter and it would have given you the same results. It was about the ohm test being a b.s. test in most automotive applications, yet that is what the manufacturer flow charts are full of. Ohm tests...or I should say b.s. 😂😂
Why do you never apply an ohmmeter to a live network??!! - An ohmmeter applies its own voltage across a circuit. If it is applied to a live network there will be the current that is already flowing plus the ohmmeter’s current. This will give an inaccurate result and can also easily damage the ohmmeter
Paul (Not Dan) I am an avionics tech by trade. I have been working on airplanes and cars for nearly 35 years. This includes teaching basic avionics to new technicians at our airline. My automotive education started with a tach and dwell meter, and for diagnostics it was a Sun Interrogator and a Simpson 260 analog meter! What you are saying here (and so many of your videos) is spot on! Many of the fundamentals roll right into the aircraft electronics world as well. I have even had a few of my guys come have a look at this video specifically. I'll be buying your book as I have started to get into working on newer cars as a side business. You are doing awesome work!
wwas the ohm reading a fair test if you didnt have the circuit loaded though? You had the key on whenever you were doing the voltage drop test. edit: i guess if you are doing a ground test....the circuit doesnt have to be loaded for a good reading.
Scanner danner is the man! 5 years out of trade school and still learning much more than shop foreman with 15 years in one make can show. Premium is on your website correct?
does the voltage drop readings increase as amperage increases?i seen a car that had a 2v drop on power side of fuel pump,the spec fuel pressure was 45psi but the pump was putting out a massive 90psi.would this cause a rise in amperage that would create a 2v drop?
Yes, absolutely you can have an excessive voltage drop on a circuit from too much current. For example: frozen electric fuel pump drawing 19 amps of current read 5v on the supply wire at the pump. Normal current would have been 4-6 amps on that system. So with 19 (from a frozen pump), the supply wire itself becomes warm (search what a PTC resistor is) and as temperature rises, so does resistance and therefor voltage drops
Another excellent video...Thanks!!! It's like one of those movies you need to watch multiple times... Working with circuit boards, so often I see where the power looks just like that jittery wave of your ground in the video (almost always a cold solder joint)...I'd say 75% of most circuit board failure issues are power-related (and often mechanical in nature)... Forget about it...considering the load of a measuring device?....Make everyone cry. Thanks again.
Now, now, now; theres nothing wrong with ohm testing....AS LONG AS YOU ENJOY WAISTING ALL DAY and wanna mis-diagnose an unloaded cicuit or bad ground. Im not an engineer but have been doing my own wrenching since the early 80's and can count on one hand the times Ive ohm tested something to find why a circuit is inoperative. Ignore the Poindexters who wanna waiste an hour or two ohm'g everything as Voltage drop is the way to go for expediency
It’s always funny that people comment that you are wrong yet never make thier own content and believe they are right no matter what. This isn’t home wiring this is auto circuits. I bet the guys not even an engineer. Thanks for sharing Paul great job on this.
There are both high and low impedance meters. Take your pick. High current equals low voltage, high voltage equals low current. Imagine two resistors running parallel in a circuit, one is one ohm and the other is one hundred ohms or even one thousand ohms. Current will flow thru both resistors. You are stating the obvious or you don't have a true understanding of electricity and magnetism. Where there is one there is always the other. Thanks but I don't need to learn anything, I have a degree from caltech. All I needed them for was to verify I know the subject. Funny, even Nikola Tesla didn't fully understand some of his experiments. Some were just plain wrong. The single most incorrect belief is that all electrons flow to ground. They do not, they flow back to where they came from.
I've seen voltage drops in battery cranking and charging grounds. One shop couldn't understand why they were changing batteries (2) in a large truck. Battery ground was at a steel plate less than 1 foot from the battery. The steel was part of a steel body bolted to the truck frame, and there was a large flex ground jumper from the frame to the engine. One new triple ought (000) cable from the battery Negative to the engine block and a 2.6 Volt voltage drop went to .7 drop during cranking. No more battery, cranking and charging problems!
Mr Danner! I bought your book years ago. Our shop is very successfull thanks to my knowledge growth. Now we made the first company dedicated to making strong, durable mechanic gear. Let me know what you think. smeargear.net
Great video Paul. As an automotive lecturer in colleges myself I regularly inherit learners/mechanics/apprentices with a sort of beginning knowledge of electrics in need of improving. This exact point - that the pittance of current pushed by a multimeter battery doesn't load the circuit, and therefore a terrible ground for example would 'pass' an ohmmeter test - is one we have to regularly cover. REPEATEDLY. :) The solutions are several - repeated examples (also I direct them to your book and vids as you know :) ); a revisited firmer command of the basics; simply getting them into the habit of saying "volt drop" not resistance sometimes helps a little too. The problem is that to a basic understanding their mistake (though still wrong) is based on 'correct' statements. So that bad ground for example. They have the following basics: "the problem could be too much resistance" "Resistance is measured in ohms" "An multimeter can measure ohms" and from those 'true' statements they draw the wrong conclusion "therefore a multimeter set on ohms can test this bad ground". To say to them "yes, in a sense the problem IS too much resistance...and I DO get WHY you would think that...but you can't test it by directly testing resistance per se like that." makes their brains hurt at first :) So as much as I (and eventually THEY too) understand why this is wrong...I do have some sympathy as I get WHY they make this basic error. BUT....That 'experienced mechanics/technicians get this wrong though...there's no excuse. And as for the 'electrical engineer' that had a go at you. ha. :)
Hi Dan I live in the UK and have been doing diagnostics since the 70s, I did 25yrs for the RAC which is like your AAA but we have dedicated patrols who now have diagnostic readers so prior to that the training centre I ran/managed had nothing but good multimeters for years which give you a good grounding for using a diag tool, and the one thing we had on a sign in the workshop was "volt drop change my life" ,because exactly what you said you can get good resisstance on circuits, coils etc even when they are bad. Keep up the good work Ian
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NEWS FLASH!! Ohmmeters will lie to you!
Between flow charts written with an ohmmeter as the tool of choice and then people telling me "you should have measured resistance on that circuit, you are over-complicating things with your methods", I've seriously had enough!
Time for everyone to learn something. Watch close and never tell me again to use an ohmmeter in a case like this.
Here is the original video on UA-cam
Poor running, flashing CEL, no codes (bad computer ground) - Toyota ua-cam.com/video/44dP6X3QS5A/v-deo.html
Here is the SD Premium video I am recommending as a follow up
www.scannerdanner.com/scannerdanner-premium-chapters/basic-electrical-concepts/485-basic-electrical-review-part-2.html
Nice video. Drives me crazy when techs say they ohmed the wires! Load it up and check the voltage!!
Honestly it wasn't my intent the bash him in particular it was just the motivation I needed to touch on a very misunderstood concept.
Keep doing what your doing we love your teaching scanner danner screw the engineers
I see same with the power pro super heros
What I learned from u is good continuity does not mean good CONDUCTIVITY Check voltage drop of the circuit current has to flow A continuity test can’t verify the ability to handle the circuit current
Fantastic demonstration of voltage drop testing Paul!
yeah, this one has been around for awhile and I keep referring people to the original video, but I cut it down to the main point :-)
Thanks Dan!
Hey dan when will you upload your video i am waiting for lots of excitement
Danny and Paul my idols.
DiagnoseDan's video coming
Hi Paul! I’m an EE and I’m not surprised at all that another EE would say that. I worked with several EEs who came out of school and although they knew the academics, they weren’t worth a crap in the field troubleshooting automated industrial equipment. I can remember asking one “How should we test this cable?” This cable was for a 250 amp DC power supply. You guessed it as an ohmmeter was his answer. Then I had to teach him about voltage drop testing which of course he never heard of. 👍
freaking awesome, voltage drop for the win !!!!! Paul how dare they try to question your skills ??? good thing you showed them !!!!! hey buddy sign up for scannerdanner premium maybe you'll learn a thing or two lol !!!!!Paul for president 2020 !!!!!
#Trump2020. Paul for 2024
If engineers had to fix the garbage they design today, things would get MUCH easier for us in the shop, that's for damn sure.
GREAT explanation as always, Paul. Great to see Caleb absorbing all this knowledge, too. He's probably already a better diagnostic tech than I, and I've been doing this as long as I can remember. 😎
I teach for a major auto manufacturer and we teach voltage drop. We even show where the resistance check will lie to you. It's all about the voltage drop or load testing.
awesome! now go tell the manufacture higher ups to stop producing flow charts with resistance measurements for main powers and grounds :-)
Archie I took 2 of your electrical classes back in 2017 or 2018 and I remember you telling the class this. To this day your classes were some of the best training I've ever had
@@jharrison6557 thank you for the kind words
I’m curious if this EE went on to explain how he would prove a bad ground with just his ohmmeter???
He did and to be fair he was not being a d-ick in anyway. It just struck a nerve for me because he quoted exactly what a manufacturer flow chart would have you do.
Engineers is the reason why techs exist. Techs repair what engineers got wrong.
Frank Gonzalez I couldn’t agree more. It seems like certain Engineers would jump over 100 virgins just to screw a tech.
Thank you thank you. Techs have to fix all bad engineering. Work for international dealer boy if the public can only see what they build. You would run the other way.
I agree some.u gotta think engineers cant think of every aspect of wat they design.its so many things that have to be factored in.do they say i wonder if i put this in this location would it be easy for the tech to repair.no.thats the reason why they r constantly changing things.its easy to blame them.those guys r brilliant.2 thats why they make more than us.
I have proven to myself that the load pro works great for such occasions. Not advertising here but the darn thing works on my meter like a charm.
I myself have used the ohm meter and misdiagnosed a simple problem.
Spot on !!
Ralf; which load pro is a good one to get ? Thanks.
@@tubetime39 I'm sure they are all good I got the Original.
HaHaHa engineers should try actually fixing cars.
Yup SD premium changed my life. Well worth every cent. Highly recommend 👍🏻
Thank you Burt!
Me too man! Money well spent.
I totally remember that Toyota video..Lol. Great lesson on why voltage drop is best. Thanks for sharing this Paul. Great video.!
Put that freaking Ohmmeter BACK in the toolbox.! 😂😂👍🍻
Cheers Brotha
Totally agree. The other down side to Ohm checks is you have to isolate the circuit. Which means disconnecting stuff & ultimately changing the circuit. The Observer Effect at it's finest (the mere observation of a phenomenon inevitably changes that phenomenon). Sometimes simply touching the wires/connectors will 'fix' the problem, sending you down a rabbit hole and possibly never finding the problem. So if you can test the circuit with the circuit untouched, you will have a higher probability of success (and probably develop less gray hairs in the process).
Hi SD. I'm also an EE and I was thinking, you can't get the required resolution using a simple ohmmeter to tell a bad ground. As you said, 30A through .1 ohms will show 3V of drop and anyone looking at .1 ohms would probably call it good.. Not to mention, the ohmmeter won't heat up a connection like current flow will. Agreed, voltage drop all the way.
I agree with your assessment that the resolution of the ohms meter isn't good enough. Paul, I'd love to see an experiment next time you run into one of these. Measure current as well as voltage drop on the bad connection. We could use ohms law to prove that there is measurable resistance there, the meter just isn't good enough to report it.
Would like to know your take on the Sullivan Load Pro leads for meters...
Mr. Sullivan likes to publically bash people, including me, so I won't comment
ScannerDanner
I can appreciate that and definitely take that onboard, thank you...
Load Pro works, but it is not the "end all" tool. I have had cases with resistance the load pro didn't detect. Happened to me recently on a BMW with a loose ground cable.
Lynx Star Automotive
Good to know...
I bought a load pro few years back,convenient because it has a button but made poorly,cheaply that is. I would never buy another.
GM teaches us how to do voltage drop, but really focuses on resistance measurements. I’ll do them on cars where I have no idea what’s going on and need to follow the flow chart (unfortunately) but your methods have really opened up my diagnostic abilities over the last year and I just wish I had more time to go through your stuff
It's there when you're ready :-) you never miss a class
Yes,we like Paul's class
That's awesome professor. It's a good feeling proving people wrong. I remember that case study u were talking about the 900 ohm of resistance on that GM vehicle with the aftermarket alarm system that the customer didn't even know was there. Great job professor. Cant wait for the navigator case study. Take care 😀
Paul, Caleb, I want to thank you two for providing such great online education, YOU TWO ROCK! (Netherlands Europa) 20:30 EST
You teach what works best for you. The do it your selfers will have to make up their own minds. Just keep teaching mate. Knowledge is all we really have to keep. Your work is appreciated.
@@foobarmaximus3506 Would you stop? Just stop.
Thank you Paul Danner for doing what you do .Please keep keeping on brother !!!!!!
Nice
Diag tech for Audi here and they teach and only recommend voltage never ohm meter
I'm a field tech for an OEM too and my side teaches DVOM circuit diag and voltage drop. However, our tech hotline doesn't push voltage drop testing or load testing as much as I would like. Hate it when I have to travel accross the country to find a lousy ground or power supply!
The EE's flow charts don't Stress, Load, or Strain the wires in question as you have by turning the key ON, and pressurizing the circuits to their normal capacity, to "catch" excessive drops in voltage with Ground- to-Ground voltage drop checks. I've heard it called 'stealing" voltage from the circuit, which in your case was the corrosion . I hope this makes your case stronger!!
Absolutely agree. Loaded voltage drop test is the way to prove wire integrity. In the electrical field the utility workers have what they call "the beast". They clamp on at the meter and seriously load the service drop. If there is a weak connection you will see a voltage drop. I might add, even on a short to ground or ground fault i tend to grab my megohm tester. A gfci trouble call can be hard to trace with a wimpy ohmmeter. Put 500 volts and ground fault shows up easy. (Not for cars) love engineers but sometimes......a little experience goes a long way! Cheers
What's a mega ohm tester? Awesome! Sounds like the tester alone could kill you?
@@ScannerDanner lol. It will tickle. A bit like the spark plug. It's actually referred to as an insulation tester. Commonly used to test motor windings. In nj, we had to megtest wiring that had not been permitted. If a nail or staple knicked a wire this would show. My fluke 1507 can test @ 50,100,250,500, and 1000 volts. I imagine on a car you could fry stuff if not careful. Same precaution as welding on a car? Cheers
@@ScannerDanner a insulation resistance (megger tester) is commonly used for testing insulation resistance on high voltage motor windings etc. It applys a large voltage to the circuit and measures the current flow to provide a resistance measurement. Unfortunately they don't suit testing low voltage systems.
That's still an awesome tool for you guys for sure.
@@ScannerDanner I've heard you say it in other videos but the ohm meter is testing at very low voltage/current. The closer the test matches real conditions the better. So, yeah you hit the nail on the head. I plan on buying a test light asap. (From your friends JB)
like you, i love an excuse to buy a new tool! Honestly, half the reason i love your channel is seeing all the cool tools! Cheers
ScannerDanner. I thank you.
Your theory on chequing the voltage drop. Am not an electrician. I don't know why people who are experienced electricians. Can see the easy practicality of your sureshot tecnique. But it sure will make second guessing. Away with the useless time wasted. You're right on the money. Ohms quantity testing - Like you said on the engine grounds going to the computer. It's a waste. Unless you take your time to inspect the conditions for a solid ground. Going to the computer 💪💪. Always checking voltage drops.
I would say. On every electrical problem is 🔑👍.
Making sure the relay is okay every time.
Using a test lead on your Power probe 4 . Go to Feed mode and touch those same points. The red or green Led will light up / annoying sound to let you know if you have a good ground or power etc...also you can read the resistance at the same time. It will not light up or sound off if there is high resistance. The PP4 will load the circuit internally like your test light. Great learning video 👍 you guys made
The PP4 mode you are describing only loads the circuit with a less than 20 ma LED bulb. It too would have failed this test
I agree with you 100%. Problem is that ohm testing is still being taught to apprentices here in New Zealand, and probably many countries. The use of an incandescent test light is not allowed here in many workshops because of the damage they cause!! Their reasoning is beyond belief. I'm sure some instructors & techs still think the world is flat!
Really appreciate ur vids man , honestly I’ve learnt so much for ur content it’s made me a much much better tech
Thank you!
I got "burned" a little using the DVM a few months ago fixing my horn circuit problem on the 1999 Silverado; the test light came to the rescue and proved I was chasing a ghost..
Only can use ohm meter on airbag systems.
Older hondas ignition coils show perfect ohms but a no start. Replace coil starts right up
Current handling wire and connections with dissimilar metals & corrosion will get you over time; happens all the time with aging "stuff"; more so in the "salt belt" areas of the country.
From Nick Ayivor from London England UK 🇬🇧 ⏰ 23.47pm 21,04,2022
Thank you very much 👍
SUBSTANTIAL Sir ScannerDanner
fact I went to Nashville auto diesel 2001 15k I learned the material now I a danner premium guy fixing a lot from his teaching. like a car or truck comes in late I kind of know what direction to go the next day so I watch mr danner premium channel at night bam the car is usually fixed with what I learned in less than a hr billed out the door if you own a car or truck worth the 11.00 to know how it works trust me it is going to break down DO YOU KNOW WHY. DANNER MAY BE ABLE TO TEACH YOU. thks paul
Man, can you put this comment on my feedback page please? Either way, thank you so much. This is what truly makes it worth what I'm doing.
Haven’t finished watching this, but great point Paul. Basically it‘s like testing resistor in circuit on the PCB board. You can have reading 20ohm of 10kohm resistor. Does it mean that resistor broken? Of course no, it just act as a conductor, therefore until there are current it wont resist anything. Voltage drops and injecting some current are crucial things during troubleshooting electrical/electronic components of the car.
I agree. I believe you should know ohm testing on a fundamental level but should master the voltage drop testing. The times I’ve mostly used ohm testing is if I think I have an intermittent break in the wiring and I would use the graphing meter on each end of the wires and start wiggling the harness.
That ground is ex-communicado
No scanner scanner, can't afford to take my 2004 Mercury Grand Marques, in to put in new electric cooling fan. My fan quit working, surfing largest snowstorm, in 50 years. Was rocking car back in forth in driveway, till engine shut down. It got hot, pcm said shut her Down! Couple hours later, it started, but engine fan never ran again. 2003-2005 Panther platform cars, use exactly same setup. Have Checked all fuses, relays, and diodes, and plugged in new fan assembly, it does not work!! Please text or call.
Voltage Drop Testing is always the way to go.
Dan Sullivan has been aware of this for many years. This is why he invented the LOADpro diagnostic tool. And this is why I bought one for myself.
It's important to mention that you should always
make sure that you have a fully charged battery and that all grounds are good and all your terminals and posts have been taken apart and cleaned and reinstalled.
The same applies to the Battery Posts the Positive and Ground Cables as well looking for Corrosion and damaged cable insulation.
The Voltage drop test will the level of Resistance in the circuit if any. Then you can investigate if the problem is on the Positive side or the ground side or is it simply a defective part that needs to be replaced.
I am one of your loyal subscribers. 👍👍
Thanks for sharing.. You are the best ✌️👍
0:51 not to make fun of the engineer or all engineers in general, i(FNG as a dealer tech) had a 15 sienna come in for a no-a/c complaint, found out it has a code for the clutch lock-up circuit(essentially something that sends the signal to the computer to request a/c operation) well this vehicle had a new clutch-coil put on at the previous toyota dealer(out of state, why they put a clutch-coil on i dont know but thats what they did) but its still not working, fixed the pin fitment issue that it had in the circuit but it still didnt work, so now i(the FNG) took out my ohm meter and said well the coil has 200ohms(it was right in the middle of spec) of resistance so it must be good, take a closer look and you will notice the wires were not routed correctly so now did i just measure the resistance of my pulley? new clutch coil and it works now, ENGINEERS! WE LIVE IN THE REAL WORLD! resistence measurement is not always the way to go, i personally try to use a test light(kinda like what SMA made in a video) but ill use the peanut bulb for circuit integrity to check my wires, im sure i will get a lot of hate for this comment
edit: curious how bright/dim the test light would have been in that computer ground before the fix, thanks again for the great content!!
Glad you taught that electrical engineer something valuable for free that he didn't learn in college.
Keep up the great work and proven information doesn't lie. :)
Sir Paul thanks for your kind teachings may GOD BLESS YOU AND YOUR FAMILY AMEN
there is a proper meter that tests circuit "resistance" while under load ;)
but I have a feeling that fella doesn't know what one is, perhaps he slept through his engineering (brainwash) degree and didn't bother to learn anything but :))
put heavy load on wire/s with test light/motor/load bank/etc. measure voltage drop point A to B, calculate the resistance from current, voltage/voltage drop.... yeah it;s best to have it on a stable current controlled supply and load bank. isn't that like engineering 101?
Since this is the latest video, I hope Mr. Danner gets to see this question which is perhaps more of an opinion. Furthermore, I hope he forgives the long post.
My second profession before I retired had been working as an electrical contractor. Mainly in residential and office building market.
The electrical system in a residential unit consists of three wires that come to the top of the house electrical panel and a GROUND wire that usually comes out of the bottom of the panel. This heavy wire connects to the house cold water pipes that are buried in the street (ground) and usually an eight (8) foot solid copper rod that is driven into ground. Called ground rod. Basically, the purpose of the ground system is to protect an occupant should a live wire touches the body of an appliance. The ground wire in an outlet or appliance, routes the live voltage to “ground” rather than the body of an occupant. Thus, preventing a heart attack.
Now the reason for this post---I know I am probably going against many years of automotive electrical charts and training books, so bear with me. Why a body of an automobile is called “ground”?
There is no connection between the vehicles body and the earth. Rubber tires prevent an electrical connection. In a simplified DC circuit; in order for any circuit to work, it requires a path for 12V positive to reach the load. It also needs a path of return to 12V negative, which are the two terminals on the battery.
The automotive engineers figured that since there is metal in the frame and body of the powertrain, it would save wire (money) to use the frame as the path for negative voltage to battery.
That is a great idea, but why call it “ground”? Why not call it chassis? After all the negative wire of the battery is connected to the chassis of an automobile.
Anything, but “ground” makes more sense in a DC system.
The health of a circuit can only be determined when it's capable of flowing the designed current at the designed voltage.
Makes total sense really. No one builds a circuit for the end-result of a resistance specification. The whole purpose of a circuit is to carry a specified current at a specified voltage.
I am a retired mechanic of 36 years on the job. I started working on cars in 1980 the first year GM had computers in cars. I did a lot of electrical work and in the early years i was factory trained. I always checked a ground with a ohm meter. You teach me something in almost all of your videos, I wish there were more teachers like you when i was starting. Anyone going into this field of work should at least subscribe to your premium channel i would have went to your classes!!!!! Thank you so much for being you, you are the best teacher anyone could ask for.
Thank you Rick!
Would using the battery negative terminal and ohm meter or voltage drop both get the same result? Was the body ground vs the battery as a test point the issue? Thank you for all you do. BTW Genuine question just want to learn.
Best driveability teacher. Makes sense always
The glob of corrosion at the terminal has a non linear resistance. That is, the resistance changes depending on the current going through it not like a piece of copper wire which has the same resistance as the current changes. That's why your meter has a diode check setting to check diodes because diodes and semiconductors have a non linear resistance curve. Most people don't realize it but the reading in diode check is actually the voltage drop across the diode. Hum. I wonder what reading you would have gotten if you were to measure your bad ground with your meter set on diode check? If the ground was good it should read zero. Meters really don't mean to lie. They can only tell you what they can see.
you guys are the best. now on with the show ❤️️ much easier to do a voltage drop test or computer ground test and leave the ohmmeter locked up. Thanks, Paul and Caleb
What do you do on a car that randomly stalls? Dealer had had it for 2 weeks, no stall. I will take it home and 2 or 3 days later it will stall. Usually happens on a very hot day with a/c on. Never has a fault code.
Good luck, seriously, they can be that diffucult
@@ScannerDanner Interesting, so if I sent it up to you, you would need good luck to find the issue?
I would turn the job down lol. But seriously, you would need test equipment hooked up and make it your everyday car with a list of checks to do for each stall and wait 3 days for the next one? See what I mean? No thanks. Need to break it more first then bring it to me. I can't drive customers cars around like that.
@@ScannerDanner in other words, sell the damn thing (i would tell the prospective new owner it has that issue). Thanks. I really do understand. Sad thing, it is a 2005 trailblazer with 50k miles and looks and drives (when it does) like a new car. Oh well, sometimes a low mileage car is worse than a high mileage one. Love your channel.
Start doing some common failure searches, this can narrow down the area of where to start testing, then get it to do it more often. Do the tests yourself and use my forum. It's free to join.
Start with a throttle body cleaning and relearn then go from there.
A bad ground is like a kinked garden hose, an ohm meter is still going to show 0 ohms and voltage on a bad ground. Put a load on the bad ground and you will see the like kinked water hose, when the voltage is not there like the supplied voltage. nice video Mr Danner.
Paul what's the best resistors to use on automotives ....
I'm also an engineer and I say use an ohm meter Danner cause does what my tech manual says!!!ohh and I confirmed that with my poodle and she suggested the same thing.
Great video Paul and nicely explained.
Voltage drop testing all the way!
Garbage in Garbage out!.. load test/voltage drop test all power supplies. Fantastic video. The engineers are the ones that make these awful misleading flow charts.
I tell people load the circuit do your volt drops see what the real problem is. Everyone pushes off diag work to me that always seems like easy fixes like that !
Excellent!
GREAT INFO PAUL! I absolutely love love love the premium channel can't get enough of it you have taught me lots of valuable knowledge even for me being a heavy duty Diesel technician , It doesn't matter I work on literally everything.
Appreciate all the hard work you put in these videos 👍🏼
This comment is awesome, thank you! Would you be willing to put this on my feedback page? Either way, it is so cool to hear how the material transcends the auto field (if that's the right wordl
@@ScannerDanner done!
Sorry i didn't know that. I know you dont need your very good at what you do. Hope i haven't offended you.
Your spot on the ohm meter does not load the circuit.
I fail to see why you need a voltage drop test, when your ohmmeter showed a problem at the 7:20 mark. At the 7:20 mark, when 0.00 was read - that number right there indicated a problem. If you check the multimeter specs, for example, a Fluke 117 will not display a resistance above 0.00, until that resistance hits 0.1 ohms. When a meter reads 0.00, this indicates a resistance so low that it's lower than the meters resolution, but it does not indicate "0 resistance" as was assumed. There's no need to continue on with a voltage drop test. That 0.0 right there tells you it's a problem.
Same reading as touching the leads together. 0 ohms = no resistance
Good job good teacher l always enjoy to listen and learn from you and thanks
hi how are you , i have a car that have a high camshaft sensor voltage , can you make a vedio about it? i cant find the problem
Excellent! So thankful a Chrysler training instructor recommended me to your channel! Time to level up my diagnostic skills from a true Pro!
Great to hear! Welcome!
SD is the GOAT
Lol I suppose that's good. :-)
One strand of copper will conduct voltage and continuity and zero ohms...BUT NO CURRENT.
You're right...voltage drop is the way.
I've been burned by ohm tests.
Electrical engineer just got burned...good content Paul
Yeah, that is a good video . I watched it a long time ago . Voltage drop is the best way to test circuits
Better in this format I think. Other than the shameless plug at the end of my channel
Circuits should always be tested under load....
A resistance test for a circuit is a totally "No" for me
I was testing a GM air conditioner system on an S10. I had power everywhere it was supposed to be, had ground too. Circuit still failed to operate when i plugged everything back in. I switched to a test light and checked my meter, power, when i touched test light it dropped to "0". All became clear, LOAD THE CIRCUIT!! It was a bad relay, burned contacts the post mortem revealed. So i am absolutely on board. I have also discovered that electrical engineers generally go by the mantra "looks good on paper", as we know, in reality outside the draft board, its all very different.
A valuable lesson, one you'll never forget
Watching every single video of yours. Wish i could have seen all your videos when you started your career. Absolutely awesome videos. Calib you are blessed to be part of your dads business. First hand info. Absolutely brilliant. Thank you very much. I am not a mechanic but do work on peoples cars. Absolutely brilliant. Luv everything. Cannot get enough of your info. You are helping so many people. Watching your video, then go to my toyota to do same tests where possible. 👏👏👏👏
With this attitude, you will succeed! Watch all the free ones here on UA-cam, then come to my website if you want more. I have about 450 more video there with half of them classroom lectures where I invite you to be part of it online. www.scannerdanner.com/join-scannerdanner-premium.html
Fantastic vid. I was working on a No Crank No Start on a Bobcat. I was convinced it was somewhere in the ignition wiring. My test light bulb was burned out and I had no spares. At the time, I didn't have a power probe. So I used my multimeter and checked the resistances instead of repairing my tool kit... shame on me. I wasted unneeded time. I eventually pulled my head from my butt and borrowed my friend's test light. I started my tests and checks all over again. I followed the voltage drop test all the way to a hidden damaged wire within a very inconvenient place in the frame that was being held together by a single strand of wire. That single strand was enough to positively test continuity but would drop the voltage.
100% my friend, good job!
Resistance testing is almost useless on any circuit that carries measurable current
You are one of the best, and you are very humble and down to earth.
You did not used a regular multimeter to measure the voltage drop, you used a scope multimeter on a high resolutin scale. I did nt see a voltage measure with the yellow meter you measured resistence. With scope multimeter the voltage drop, varies very much in time (50 milisec), and the amplitude goes from -2 to 8 V so fast that the normal meter on DC scale will never show. Maybe a True RMS on AC would show someting. So, if we do not have a scope meter or a True RMS meter, what can we do ? Nice demonstration , thank you :)
The average of that signal was showing on the screen too. There was a min, max, and current digital reading. It would have definitely shown on a regular digital voltmeter. But good point about averages and some things can be missed. Not this one though. Thanks!
Why not both? I mean it ain't hard with a meter to just swap between the two and turn the car on and off. I feel like that would be a good way to just make sure you catch everything but good to know if I can only do one volt drop
For sure, you need the ohmmeter at times. In particular with CAN network disgnostics. But why is it good there? Because those are basically non current carrying circuits. So anything that has measurable current flow, the ohmmeter can test good but still be bad.
Many good points here and I'll make a point too. Comparing a low cost/accuracy multimeter to a high cost/accuracy scanner/oscilloscope isn't fair. And I'm with you on volt drop testing too.
it wasn't about a low cost meter. You could have used a fluke ohmmeter and it would have given you the same results. It was about the ohm test being a b.s. test in most automotive applications, yet that is what the manufacturer flow charts are full of. Ohm tests...or I should say b.s. 😂😂
yes voltage drop is the way to go
yes then i have more work. truly my low pro work great!
Why do you never apply an ohmmeter to a live network??!!
- An ohmmeter applies its own voltage across a circuit. If it is applied to a live network there will be the current that is already flowing plus the ohmmeter’s current. This will give an inaccurate result and can also easily damage the ohmmeter
I've never, not once, seen an ohmmeter damaged by measuring a circuit that still had source voltage on it. It simply gives an inaccurate reading.
Paul (Not Dan) I am an avionics tech by trade. I have been working on airplanes and cars for nearly 35 years. This includes teaching basic avionics to new technicians at our airline. My automotive education started with a tach and dwell meter, and for diagnostics it was a Sun Interrogator and a Simpson 260 analog meter! What you are saying here (and so many of your videos) is spot on! Many of the fundamentals roll right into the aircraft electronics world as well. I have even had a few of my guys come have a look at this video specifically. I'll be buying your book as I have started to get into working on newer cars as a side business. You are doing awesome work!
Thanks so much! I really like hearing how the info rolls into other fields. This means a lot
wwas the ohm reading a fair test if you didnt have the circuit loaded though? You had the key on whenever you were doing the voltage drop test.
edit: i guess if you are doing a ground test....the circuit doesnt have to be loaded for a good reading.
No! (First question) the ohmmeter missed it. And the ground was loaded with the key on, it was a ground to ground voltage drop test. (Circuit loaded)
That's some strong medicine.
Scanner danner is the man! 5 years out of trade school and still learning much more than shop foreman with 15 years in one make can show. Premium is on your website correct?
That is correct. Thank you so much! I look forward to hearing more form you on the site.
does the voltage drop readings increase as amperage increases?i seen a car that had a 2v drop on power side of fuel pump,the spec fuel pressure was 45psi but the pump was putting out a massive 90psi.would this cause a rise in amperage that would create a 2v drop?
Yes, absolutely you can have an excessive voltage drop on a circuit from too much current. For example: frozen electric fuel pump drawing 19 amps of current read 5v on the supply wire at the pump.
Normal current would have been 4-6 amps on that system. So with 19 (from a frozen pump), the supply wire itself becomes warm (search what a PTC resistor is) and as temperature rises, so does resistance and therefor voltage drops
Yes you did it with your experience 🤍
Another excellent video...Thanks!!! It's like one of those movies you need to watch multiple times...
Working with circuit boards, so often I see where the power looks just like that jittery wave of your ground in the video (almost always a cold solder joint)...I'd say 75% of most circuit board failure issues are power-related (and often mechanical in nature)...
Forget about it...considering the load of a measuring device?....Make everyone cry. Thanks again.
Good job good teacher thank you
Now, now, now; theres nothing wrong with ohm testing....AS LONG AS YOU ENJOY WAISTING ALL DAY and wanna mis-diagnose an unloaded cicuit or bad ground. Im not an engineer but have been doing my own wrenching since the early 80's and can count on one hand the times Ive ohm tested something to find why a circuit is inoperative. Ignore the Poindexters who wanna waiste an hour or two ohm'g everything as Voltage drop is the way to go for expediency
It’s always funny that people comment that you are wrong yet never make thier own content and believe they are right no matter what. This isn’t home wiring this is auto circuits. I bet the guys not even an engineer. Thanks for sharing Paul great job on this.
Paul, great video!!!!!!!!!!!!! Flow charts are like chasing ghost's down rabbit hole's!!!!!
There are both high and low impedance meters. Take your pick.
High current equals low voltage, high voltage equals low current. Imagine two resistors running parallel in a circuit, one is one ohm and the other is one hundred ohms or even one thousand ohms. Current will flow thru both resistors.
You are stating the obvious or you don't have a true understanding of electricity and magnetism. Where there is one there is always the other. Thanks but I don't need to learn anything, I have a degree from caltech. All I needed them for was to verify I know the subject.
Funny, even Nikola Tesla didn't fully understand some of his experiments. Some were just plain wrong.
The single most incorrect belief is that all electrons flow to ground. They do not, they flow back to where they came from.
I've seen voltage drops in battery cranking and charging grounds. One shop couldn't understand why they were changing batteries (2) in a large truck. Battery ground was at a steel plate less than 1 foot from the battery. The steel was part of a steel body bolted to the truck frame, and there was a large flex ground jumper from the frame to the engine. One new triple ought (000) cable from the battery Negative to the engine block and a 2.6 Volt voltage drop went to .7 drop during cranking. No more battery, cranking and charging problems!
Engineers can be a pain in the butt.
Well Done!!! 👍👍👍👍
Mr Danner! I bought your book years ago. Our shop is very successfull thanks to my knowledge growth. Now we made the first company dedicated to making strong, durable mechanic gear. Let me know what you think. smeargear.net
Proof that "Resistance testing is FUTILE" !
yes sir! When an ohmmeter measurement is bad, it is bad, but when an ohmmeter measurement is good, it can still be bad lol
Great video Paul. As an automotive lecturer in colleges myself I regularly inherit learners/mechanics/apprentices with a sort of beginning knowledge of electrics in need of improving. This exact point - that the pittance of current pushed by a multimeter battery doesn't load the circuit, and therefore a terrible ground for example would 'pass' an ohmmeter test - is one we have to regularly cover. REPEATEDLY. :)
The solutions are several - repeated examples (also I direct them to your book and vids as you know :) ); a revisited firmer command of the basics; simply getting them into the habit of saying "volt drop" not resistance sometimes helps a little too. The problem is that to a basic understanding their mistake (though still wrong) is based on 'correct' statements.
So that bad ground for example. They have the following basics: "the problem could be too much resistance" "Resistance is measured in ohms" "An multimeter can measure ohms" and from those 'true' statements they draw the wrong conclusion "therefore a multimeter set on ohms can test this bad ground". To say to them "yes, in a sense the problem IS too much resistance...and I DO get WHY you would think that...but you can't test it by directly testing resistance per se like that." makes their brains hurt at first :) So as much as I (and eventually THEY too) understand why this is wrong...I do have some sympathy as I get WHY they make this basic error. BUT....That 'experienced mechanics/technicians get this wrong though...there's no excuse. And as for the 'electrical engineer' that had a go at you. ha. :)
Hi Dan I live in the UK and have been doing diagnostics since the 70s, I did 25yrs for the RAC which is like your AAA but we have dedicated patrols who now have diagnostic readers so prior to that the training centre I ran/managed had nothing but good multimeters for years which give you a good grounding for using a diag tool, and the one thing we had on a sign in the workshop was "volt drop change my life" ,because exactly what you said you can get good resisstance on circuits, coils etc even when they are bad. Keep up the good work Ian