Multimeter basics, voltage and resistance tests (a free SD Premium video)

Watch this case study to see this theory being applied! • Voltage Drop vs Resist...
Why does current need to be flowing for accurate voltage measurements?
What is the difference between a regular voltage test and a voltage drop test?
Why is the ohmmeter not a good tool to use for finding resistance problems on high amperage circuits?
Engine Performance Diagnostics chapter 1 page 23
Playlist
- (Chapter 1) Misfire ID, Compression Tests, Vacuum Leaks, Fuel Trim, Head Gasket, Restricted Exhaust, Low Power, DMM
• (Chapter 1) Misfire ID...
Related videos
- How to test a starting system (Mini Cooper Case Study)
• Engine does not crank ...
- Engine does not crank (Cadillac with a bad block ground)
• Engine does not crank ...
- How to test a starter (engine doesn't crank)
• How to test a starter ...
- No Crank Diagnosis (how to troubleshoot starting system problems) • How to troubleshoot a ...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

[@jerrodwilliams6789]

That was anything BUT a weak analogy. At 32:29 all my electrical fears subsided and everything came together and fell into place. This video in 2012 made me a permanent subscriber and I am now an ASE master technician AND a L1 TECH thanks to YOU!

[@TOMAS-lh4er]

im 65 retiered and know nothing about electric but now i can actualy learn thank you for your teaching please leave all these older vidios availabel to wach ive always thought i wasnt smart enough to do electric stuff, but i understood this vidio i cant wait to watch all your vidios god bless you thomas in tucson

[@vyse128]

I could watch electrical theory videos all day. Love it, always good to brush up on the basics. Being a 12v technician, you would be amazed at how many people in my field don't know how to use a DMM even, let alone do a voltage drop test.

[@jeremystice5694]

You are a huge blessing and making huge impact in this world 🌍 thank you helped me understand so much and I have my A/s degree in automotive technology and you have taught me things I was never taught or didn't pick up correctly in school. I wanna thank you for all you do for this industry

[@jeremyshanks6937]

I have used the Load Pro for a couple of years. It is my GO-TO tool for loading a circuit. It is very useful in finding a restriction in current flow due to high resistance. It allows you to check the voltage while circuit is loaded, or not loaded. Another great video.

[@eramirez198121]

But it can only be used on 12volts or does it also work for low voltage wires? Like say one that only sends 5v source?

[@MrJgonzalez2]

I had a hard time checking grounds with a voltmeter, I finally got it, the voltmeter reads difference in voltage so battery ground is already 0 volts, when you check another ground there should be minimal difference,thanks Paul Danner for making all you videos extremely educational.

[@majstorivan84]

First of all I wish to thank you because your videos helped me so much to speed up fixing time and make it possible to determine bad ground,wiring,feed.... I am a self-learning in the field of electric problem.You make it so easy to understand.Keep up the good work!!!

[@bwcordes]

You're a heck of a teacher. I've been watching this video just to hear your style. Great work.

[@wyattoneable]

Your book by it self is good. Your book with the videos is excellent! With your input I'm able to take better notes and things are starting to make sense.

[@andyd9971]

There’s good teachers out there and there’s few great teachers, you one of the great teachers, thank you for sharing your great knowledge with us

[@ScannerDanner]

Thank you so much!

[@James-fs4rn]

👍 You're a great teacher Paul! Thank you for sharing.

[@elebeu]

Awesome videos. I know most of this already but this and your other videos are clarifying some things.

[@thrasher305]

Amazing video. Concise and well explained. Thank you Paul!

[@macafy100]

It couldn't be more clear thanks man.

[@monkeywrangler5200]

Very nice explanations. You’re a really good teacher.

[@ScannerDanner]

Thank you, I'm glad you liked it

[@gravey07]

I found the 1999 Ford Ranger bad ground video is very good to help understand these voltage drop checks having watched this. Now pass this man a beer.

[@SuperCarfix]

I love this video,the best explanation of ohms low ever. thank you

[@richard1835]

I am now able to understand more about Voltage Drop Testing. Thank You,

[@peternajduk7841]

Dude, i finally got it! After the 17 minutes in this video I got the aha moment. Thank you

[@malcolmyoung7866]

Many thanks for this video, Paul....very informative...

[@trathehandymanchicago1976]

i'm going to watch this over and over thank you your kickin science on this lecture!

[@ScannerDanner]

I have hundreds more just like this on my website if you're interested www.scannerdanner.com/join-scannerdanner-premium.html Thanks so much!

[@seth.wright]

Your videos are the best on KZbin for auto electric work you have saved me thousands of dollars over the years in parts I didn't change in search for a wiring problem thank you for sharing the knowledge.

[@ScannerDanner]

Here you go eautorepair.adtrk.biz/?a=10817&c=24&p=r&s1= It's $20 for an individual car and it is the same service information and diagrams i use, only black and white. But still good. Thank you so much too for the comment!

[@seth.wright]

@@ScannerDanner thank you so much Im always looking where to get the best wiring diagrams

[@ScannerDanner]

that is awesome man. thanks for the comment and I am glad you got it. that is exactly right

[@ingascheib8873]

This is amazing. I wish I was taking your class. Thank you so much for sharing your knowledge.

[@ScannerDanner]

You can! I have all of my classes recorded and they're available on my website here www.scannerdanner.com/join-scannerdanner-premium.html Hope to see you there!

[@ScannerDanner]

A floating ground provides the computer with a cleaner signal and is particularly useful for low voltage circuits. You could say it keeps the voltage sensing circuit for that particular sensor away from the noisy engine block ground. O2 sensors and variable reluctance sensors use ground bias voltage a lot. I have also heard it has to do with the analog to digital converter too, but I am no electrical engineer.

[@johnramos6318]

I spent a year and 32k and you showed me more stuff in a few videos than they did now I know for sure I was scammed by that trade school you are a awesome teacher and fun too watch

[@ScannerDanner]

Thank you John! I have 500 more videos like this on my website too if your interested in joining. www.scannerdanner.com/join-scannerdanner-premium.html

[@ScannerDanner]

@Turbotomass i don't recall talking about an ECT in this video but either way with no ground there is mo current flow and therefore no voltage drop.

[@bell92661]

GREAT VIDEO! FINALLY UNDERSTAND :) BEST VIDEO IVE FOUND RELATING TO ELECTRICS THANKS

[@steveguest8028]

Hi Paul,again very good explanation of what voltage drop is and how to test for it....Thank you for another excellent video 👍🏻

[@donniejohnson7499]

Load pro test leads. I got some that was give to me. Only thing I've used them for is the hollow point on test leads. Great for checking pins. That's all I can say about them. I check for voltage drop at load. Great video Paul Danner.

[@donniejohnson7499]

Paul Danner. Awesome video. Basic Electrical fundamentals is a must.

[@ScannerDanner]

It sure is! Thank you!

[@ScannerDanner]

@apodlosky Yes, This was in Section 1 "Universal Testing Methods"

[@robertpope3619]

That wasn't a weak analogy at all Paul. That made great sense.

[@vosaemify]

dude!! i love that you teach me sooooo much

[@nickayivor8432]

Very KNOWLEDGEABLE Thank you 🙏 Sir ScannerDanner From Nick Ayivor from London England UK 🇬🇧

[@ThunderbirdRocket]

Ultimate training ! Thanks !!

[@ScannerDanner]

Thank you!

[@mrexecutive1]

Outstanding educational video! much like your others.

[@davidparker667]

Wow..that is the first time I have fully understood those principles. Thanks!!

[@ScannerDanner]

Awesome! Thank you. I have hundreds more just like this both here on YT and on my website. www.scannerdanner.com/join-scannerdanner-premium.html Hope to hear more feedback from you as you go

[@davidparker667]

Thanks, I will definitely be looking at more. I wish I had somebody explain things so clearly 20 years ago. I'll definitely be buying your book soon!!

[@hmarmobiletech8332]

I would love a video from you about the e.s. electronics specialties load pro unit. I wanna get to know how to use it better. Thanks for all your informative videos!!!

[@MitzvosGolem1]

I use a battery load tester on battery cables simulates load of starter cranking 400 + amps maintain 10.5 volts minimum. Excellent work Thanks

[@jeremyhiatt573]

Nice work, thank you !

[@confidential8738]

Wow another valuable lesson learned from u. Still cant thank u enough for all the knowledge.

[@ScannerDanner]

Thank you!

[@craigbaggett3370]

Very good analogy 😊

[@johnuribarri1456]

Paul Danner i have bought your ebook :) . you my friend is a special teacher. you are very smart and realistic. i also like to say that it was cheap to buy with the knowledge you give out. keep up the good work and thanks for sharing your knowledge !!!!!!!!!!!!!

[@johnuribarri1456]

also i like the way you use your videos to help understand your book i have never seen that before and it is effective !!!!

[@ScannerDannerPremium]

Thank you!

[@jerrodwilliams6789]

He is the reason I am an ASE L1 certified Master Technician

[@ScannerDanner]

@Amopower Yea, I don't like the resistance test on those either. I prefer a scope and an amp probe or voltage waveform. But you could still do a resistance test, it is a low enough current circuit that it should be accurate. An ohm test would be especially useful with an open coil, but then again voltage would identify the same thing. I just wanted people to understand the limitations thats all

[@MrSexy0000]

Hey 👋🏼 there scanner-Danner... I just thought 💭 I had to let you know that I think your the man when it comes to the diagnosing electrical circuits... I’m so blown away at your knowledge and test and even when you get stuck you have A test and temporary theory to backtrack your way to victory... I travel a lot and I’d love to meet you let me know what you think 💭 I’d love to learn from you like your sons..💯I don’t even think they really knowhow much knowledge your throwing out and the Benefit of retaining the knowledge to help you through life... if you want you can hit me up I sell cars 🚘 now and now I’m trying to up my mechanic 👨‍🔧 knowledge as much as humanly possible and your the best teacher 👨‍🏫 I’ve ever seen hands Down your not boring because you show hands on what your taking about and don’t take long...to you my brother I salute you...👀👌🏼💯

[@ScannerDanner]

You can have low battery voltage during a crank from: weak battery, starter motor drawing to much amperage (seizing up), internal engine problems (engine seizing up). So low cranking voltage is usually from a weak battery but don't forget about the other variables.

[@jonathanparker5721]

I think he made a couple very good points here. First that the voltage drop had to be tested with the switch in the crank position. Second that the ohmmeter is not a good tester for higher amperage circuits. It definitely helped clarify these things for me.

[@ScannerDanner]

awesome! Now watch this one to see this theory in action kzbin.info/www/bejne/g5TWf4KAq8ljl9E

[@robe5000]

oooook, i don't have one either but ive been looking into the tool for a while, and i was pretty much sold until i came across this video, and im watching it and thinking the loadpro would be great for some of the stuff your talking about testing in this video, the theory of the tool seems simply enough, i'm gonna give it a shot anywho, thanks for the reply, love your channel BTW

[@khurramali007]

you are a good teacher Scanner Danner...

[@retroguitarmaster]

you are the best teacher

[@ChicoDeon]

YOU ARE THE MAN

[@ScannerDanner]

thanks Eric!

[@jayhook-zm1pw]

just saw this. very interesting. and almost understanding.

[@ScannerDanner]

thank you very much

[@regonalbaldwin]

Thank you so much!

[@kjellgerry]

Awesome stuff!

[@ScannerDanner]

@fivefortyeye540i Yes, the circuit is ground side switched and no, you would have shown 12v on the PCM control wire because it wasn't grounded yet (no current flow=no voltage drop across the relay coil). I re-checked the diagram and with cooling fan 1 disconnected you would have read nothing (no power, no ground) with your powerprobe on the load side fan contact (pin 87).

[@aaronarmelin616]

hey paul great video. I got your paper book as a birthday gift last November. been reading though it quite a bit lately and watching the videos as I go. Me and electrical do not get a along. till I got to this video, it helped me understand more about electrical now will have to watch it more to get more. but sure helped. Also as I get into electrical more, what do you think is the best most reasonable priced dvom or would a power probe do the job? keep the great videos and I'll keep watching. God bless

[@hinojosa552]

Excellent analogies

[@ScannerDanner]

thanks man!

[@kiddbrother3]

great video!

[@laos1001]

Amazing!

[@Mangeshprajapatiprajapati]

Nice explanation

[@shaffere33]

I was a toyota tech for 11 years now working for independent shop and its a new ball game your vids keep my mind fresh on all my training. thanks!

[@mikewithers7685]

Thanks paul for another great video. Im an old dog trying to learn new tricks. Ive been out of the field since 1997 and am getting back in. your videos are helping me ten fold. Im buying your e book as soon as I get some extra cash.One question I have on voltage drop testing the + batt cable. What is the allowable voltage reading on the + cable to call the cable good,or do you always want to see 0 v during crank? I wish this kind of tranning was available back in the day lol !!!

[@PaulCTownsend]

Good job

[@aldoalduvinhernandezzavala8036]

you are the best

[@ScannerDanner]

@MrLoboreview That is correct

[@RepairRenovateRenew]

most important part - there must be 0 voltage present in the circuit to do a correct resistance test because of the way a multimeter calculates resistance. some stuff can only be learned in a classroom. good stuff

[@felplayvina]

Hi Mr Paul at 35:00 you said some tech will said bad fan motor and your right, I was working at gmc van the ac fuse keep blow it, the mechanic said bad blower motor, what I found corrosion at the motor relay but I thought the resisted blow the fuse? but never sure, thank you for this class now I understand more about corrosion..

[@30YearOldBunta]

I got my notes out again Danner, I will fix this backwards japanese wiring.

[@serchmarc]

hey paul im watching all your videos ,i hope im your 1st virtual ,long distance,peruvian student. hahaha regards from peru.

[@alanbendell5986]

Great videos Paul. my question, why when touching your probe light on signal wire - was it not sending 12v down the wire to the ecm and frying it.

[@renesabre3786]

thanks a lot good vids

[@ScannerDanner]

I really appreciate this comment. Thank you!

[@ScannerDanner]

Thanks man, just be careful with the relay coil drivers. I think the tool sounds pretty cool too.

[@pabloarevalodelaguila8767]

FIEL SEGUIDOR, GRACIAS.

[@user-pe8lm2qk8u]

I`m korean you`re video greats!

[@ForTheManDIY]

I have a KZbin video that compliments this video and explains more about voltage drop. Just search for "ohms law automotive dc circuits" and you will find the 4 videos that explain ohm's law and voltage drops in more detail. Hope this helps for those who want to know more.

[@jamesbarratt593]

I just read that the max a computer ground should have as voltage drop is .10v but what does that figure mean? 1.000 is a thousand milliamps being 1 amp, so .10v is it a tength of an amp but then what’s the ‘V’ part of it?

[@KStewart-th4sk]

+lwgraves I found your way of calculating ohm's law long and tedious compared to how I was taught which was this way: kzbin.info/www/bejne/gWi9ooGKp9KWd7c A whole 59 SECONDS! Cover the one you are looking for and you are left with the equation to use. Simple!

[@williamhaines856]

very good

[@ozzstars_cars]

awesome

[@MrFishface5]

I had a Chrysler Pacifica that would crank and run at times and at times it would not crank. I had power at the starter and also had signal voltage while cranking to the solenoid. So I put a starter in it and it would not crank it would just click after doing that. And what I found was a braided ground going from the trans to the frame that was broken.

[@ScannerDanner]

@fivefortyeye540i OK, I looked up a 98 Buick Century 3.1 There are three cooling fan relays. Which one were you checking? Also in case you didn't know this system runs the fan motors in series to each other for low speed and in parallel for high speed. Depending on your testing if you had one fan disconnected it could change the readings you were expecting to see

[@ScannerDanner]

@Bonfield2002 No, never heard of them. What are they and how do they work?

[@ScannerDanner]

@fivefortyeye540i So with the relay plugged back in is when you did this? If this is the case be very careful that those wires do not touch each other. You could fry the PCM driver. Anyway with the relay plugged in you should show 12v on three legs. 1 = control side power 2 = control side switched ground (not grounded yet) 3 = Load side power. The fourth wire is the load side feed to the fan. With the relay off this wire would show a ground (unless you had the fan unplugged)

[@ScannerDanner]

@ScannerDanner What are we working on? Year, make and model would help me help you more

[@atifabusalim7217]

Thank you Very nice vedio I think must be teaching in all unversity Again More thank for you

[@ScannerDanner]

Thank you so much! If you want more of this type of training sign up for my premium classes here: www.scannerdanner.com/join-scannerdanner-premium.html I offer a 14 day free trial

[@michaelpatosa]

Hey Mr. SD, Is it possible to use the Voltage testing method on (Airbag Circuits) like Impact sensors and any other airbags?

[@dandearman2871]

Yes. Your digital meter measuring resistance may not show you the problem in the battery cable not because the resistance can't be measured but because the meter is not designed to measure low resistances accurately. For example with some spit ball numbers. If your cranking amps are 50 amps and the cranking voltage at the starter is 10 volts, ohms law says the starter resistance is 10 V/50 A=.2 ohms so if you had even 1 ohm of resistance in you battery cable to the starter, the current to the starter is now only 10 V/1.2 Ohm=8.3 amps but now there is 8.3 A X 1 Ohm = 8.3 V across the battery cable which you can measure easily with the digital meter and that's how an ohmmeter works. The meter supplies a known current to the resistor being measured on meter leads and reads the voltage across the leads and the voltage reading is converted to resistance. They do make ohm meters that will accurately measure resistance in the 0 to 5 ohm range.

[@ScannerDanner]

@Amopower Potentiometers yes, variable speed fan no. Honestly, I rarely use my ohmmeter.

[@SteveRobReviews]

Voltage drops are a must in diagnosing and I am curious to know if you do use the LOADpro® Dynamic Test Leads. I use mine all the time and saves me a lot or time.

[@blarson1]

Thanks again Danner, I'm having a problem with a 86 blazer TBI setup and have put this knowledge to use. The CEL is constant and will not blink when the diagnostic pins of the ALDL are shorted. Rather than put in another ecu immediately I decided to confirm that the wiring isn't a problem. I have 3mV voltage drop at my ecu ground to chassis ground and upto 300mV on some of the other pins that according to the factory service manual should be 0. Would you consider that a problem? Thanks!

[@felplayvina]

Mr Paul if I checking the battery during cranking if I read less them 10 V that it be bad battery or there are different batteries reading..

[@ScannerDanner]

@fivefortyeye540i 85 and 86 will show 12v with the circuit off. So the wire you showed nothing on wouldn't have been either of those. Pin 30 = hot all the time and Pin 87 should have indicated a ground with your power probe because it would have found a path through the fan motor brush contacts to ground. This is why I don't like the power probe. It is NOT a ground even though it shows it as a ground. If the fan was unplugged then pin 87 would have shown neither power or ground.

[@kevinjarrells4385]

is there information available to tell you the duty cycle of these components so that a person could calculate expected readings on a meter?

[@scrappydogfinance8434]

I like the water pressure examples and adding hypothetical restrictions (resistance_) into a water line and asking what would that do to the pressure(voltage) at that point.

[@ScannerDanner]

@Username64870 Not necessary to do if you voltage drop test your ground circuit and it is ok. To test alt. ground, run engine at 1500-2000 RPM with all accessory loads on. Connect DMM from alt. case to battery negative post. The closer to zero volts the better. I would say no more than a few hundred millivolts difference max.

[@ScannerDanner]

@Turbotomass which part are you talking about.