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

[@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

[@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

[@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.

[@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.

[@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?

[@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!!!

[@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.

[@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

[@bwcordes]

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

[@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!

[@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!

[@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

[@robertpope3619]

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

[@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

[@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.

[@peternajduk7841]

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

[@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.

[@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.

[@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!!

[@donniejohnson7499]

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

[@ScannerDanner]

It sure is! Thank 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.

[@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

[@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!

[@Nudnik1]

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

[@ScannerDanner]

Thank you, I'm glad you liked it

[@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!

[@macafy100]

It couldn't be more clear thanks man.

[@monkeywrangler5200]

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

[@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

[@James-fs4rn]

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

[@nickayivor8432]

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

[@SuperCarfix]

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

[@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

[@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..

[@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]

@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).

[@elebeu]

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

[@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!

[@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

[@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.

[@ScannerDanner]

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

[@30YearOldBunta]

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

[@khurramali007]

you are a good teacher Scanner Danner...

[@steveguest8028]

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

[@ScannerDanner]

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

[@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.

[@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.

[@nelias7306]

Just diagnosed an 02 honda civic using this method. It had intermittent flickering of the instrument panel lights, srs light would turn on then turn off and resetting of the spedometer/tachometer during driving. No stalling, no engine codes. It would happen at least 3-4 times while driving it. I had changed the alternator/battery a year ago. I started at the battery. Terminals were highly corroded along with grounds so I tried to find a good ground and then tested power side under load with car running. There were two power cables, one said a consistent 13volts, the other went everywhere. Ok so i thought either corrosion or bad connection. Went to the distribution block where they went to, same thing... one lead had a steady 13v the other went everywhere. So there was not a steady voltage to one circuit. i was going to try and clean the lead. The lead fell off the wire while loosening it. Put on a new one and cleaned up the grounds just in case and put some anti corrosion spray on all the connections. Test drove it and no more srs light on/ instrument panel resetting. If i did not test these i would have probably went and bought a new instrument panel for nothing :) was going to test the alternator but no more issues. Im saying issue solved

[@ScannerDannerPremium]

Nice job! Thanks for sharing

[@nelias7306]

ScannerDanner Premium thank you! Also worth mentioning is i checked the grounds which were all good

[@ScannerDanner]

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

[@ScannerDanner]

What other pins are you reading 300mv on? If these are sensor grounds, then yes it is too high. You want less than 100mv on a sensor ground and less than 50mv on an ECM power ground. (That would be tested with the key on engine off or running, NOT cranking)

[@ScannerDanner]

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

[@import0408]

Matco sells what's called a volt pro. It dynamically loads the circuit. I particularly like it cause you do not have to turn your component on. similar to the load pro. Have you heard of it?

[@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 !!!

[@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

[@serchmarc]

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

[@retroguitarmaster]

you are the best teacher

[@confidential8738]

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

[@ScannerDanner]

Thank you!

[@ScannerDanner]

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

[@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)

[@thrasher305]

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

[@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!!!

[@ThunderbirdRocket]

Ultimate training ! Thanks !!

[@ScannerDanner]

Thank you!

[@ScannerDanner]

Ok, lets take a relay driver for example. The normal current draw of a relay coil is 100ma. Will 500ma be 5 times more current flow than this circuit usually sees? Yes! Will it cook the driver? Probably not, most drivers can handle way more current than the normal circuit draws. Also some are protected with current limiting devices. (Check out my GM shorted injector videos). I still wouldn't want to load a relay coil driver with 500ma.

[@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

[@ScannerDanner]

I really appreciate this comment. Thank you!

[@ScannerDanner]

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

[@johnbriscoejr9738]

ScannerDanner, I have learned sooooooo much from all your videos. You are the master!! I also watch some automotive shows on Velocity and believe this......I have not even learned a scratch about cars compared to what I have learned from your videos. Question: why you don't pitch your automotive-mastery knowledge of electrical diagnosis to a TV producer? You are a treasure trove of automotive-electrical/mechanic knowledge and putting that on TV would be very, very awesome!

[@ScannerDanner]

Thanks so much brother! That would be cool. Don't forget to check out my premium channel. I have over 350 videos on that channel now with more than 200 of them being a lecture style like this. You will not be disappointed!

[@johnbriscoejr9738]

Two thumbs up to you, Master ScannerDanner!!

[@johnbriscoejr9738]

Master ScannerDanner how do I get to the other videos on your premium channel?

[@ScannerDanner]

Where are you located? KZbin has placed country restrictions on the paid channels. There is a way around it using a VPN though.

[@johnbriscoejr9738]

GM ScannerDanner, sorry just getting to your message kids graduated yesterday. I live in Washington, DC

[@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.

[@craigbaggett3370]

Very good analogy 😊

[@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.

[@bell92661]

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

[@kennethyeoman776]

What we don't know is what voltage we have from the ignition switch. And if we have a break in either wire going to the ignitor. and the same on the negative side of the coil. we have two wires the either of them could be the cause. It could be bad igniton switch as well.

[@malcolmyoung7866]

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

[@Amopower]

I've also heard that resistance should be measured to determine if your IAC motor is fine. Not sure how you would do a voltage drop test on that one, I think those are a little more complicated because the voltage they receive gets varied by the ECU. I guess if you know what strategy your IAC is working on (like warm idle), and you know from the specs that the duty cycle should be 75%, then I suppose you could determine the voltage should be 75% of battery voltage...just thinkin out loud...

[@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

[@jayhook-zm1pw]

just saw this. very interesting. and almost understanding.

[@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..

[@MiniH0p]

holy shit man so many light bulbs going off right now. im in shock this is free

[@ScannerDanner]

Thank you! Glad you found me

[@kc360awareness]

Finding ScannerDanner has been a life changing event for me too. Learn the basic fundamentals and you’ll never regret it.

[@ScannerDanner]

@Turbotomass which part are you talking about.

[@fivefortyeye540i]

Yes, one fan was unplugged , when I probed the harness I did have a ground neg probe lit off, but on second wire no power. So dose that make it power side switched?? Yes I had 4 wires running to top of relay, I had power on 3 legs. Nothing on forth leg, looking at relay schematic writing was facing outward. The first leg going at the top going left to wright is the one that did nt show anything.. The rest had power 12 volts..

[@zvonimirbobicex-4962]

you should ve mentioned that thermistor(ECT sensor)... as being NTC...heats up, resistance goes DOWN...but the SIGNAL voltage will also go down(if the circuit is ok)...i m making comparison to that voltage drop at the fat wire(as it heats up too, resistance goes UP)...another topic...just connecting the dots...kink in a hose...what happens before and after the kink?...or kinks...got ur book, i m learning ;)

[@ScannerDanner]

+Zvonimir Bobic yes you are and thank you!

[@휘센0187]

I`m korean you`re video greats!

[@fivefortyeye540i]

@scannerdanner I guess the probe did confuse me. Why I had power 12 volts on 3 legs with koeo . So on the 98 Buick 3.1L the control relay is ground switched?? Now I'm comtiplating the future of the powerprobe .. I'll know by trashday.

[@Mangeshprajapatiprajapati]

Nice explanation

[@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.

[@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!

[@ChicoDeon]

YOU ARE THE MAN

[@ScannerDanner]

Thank you

[@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?

[@ScannerDanner]

I think one of them is used solely for cooling fan control but I am not 100% on that.

[@layahit]

Do you know what high voltage has advantage on low voltage when it comes to heavy electrical loads?

[@ScannerDanner]

a voltmeter does not support current flow. and you never connect a voltmeter in series. it is always connected in parallel. your second point is valid, to a point. If the window motor is open then you are correct, there is no current flow so when testing the ground circuit for a voltage drop it will be inaccurate. lets say your ground is open on the window motor circuit, if you unplug the connector to do you voltage testing you will miss it. so on principle, leave it plugged in

[@mrexecutive1]

Outstanding educational video! much like your others.

[@Amopower]

So would you agree that resistance readings are still valid when checking fuel senders (potentiometer), as I would imagine those are low current circuits ? Not sure about a variable speed fan, that might be some decent current.

[@Turbotomass]

What do you think about the load pro test leads where pressing the button on the pos. lead simulates a load so you don't have to worry about cranking or switching on the load.

[@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.

[@lukeclinch9928]

Hi Paul, If the car wasn't cranking due to a bad block earth what would the drop test on the power cable to the starter show? Also to show a bad earth would i just probe between the block and negative terminal on the battery?

[@MrJgonzalez2]

Paul, What is the most voltage drop allowed at the battery cables when measuring from pos terminal to starter and from neg terminal to engine block during cranking???????????????

[@hinojosa552]

Excellent analogies

[@fivefortyeye540i]

@scannerdanner I'm studying page 73 (testing computer driver) to reiterate, on that cooling fan circuit on that 98 Buick century 3.1L . For argument sake If I wanted to test that driver I simply would have hooked up test light to batt pos and touch on recessed (relay out the loop ) terminal that is ground side switched. Test light should have lit correct?