Voltage Drop, Do We Really Need To Know It!?

We always here about voltage drop in the classes we go to but does it ever really apply to fixing cars? It is always taught but never really shown in real life examples. Well any one who watches my channel knows I have shown in several videos why it is so important and how to use your meter to see the "pressure" difference between two points. Hear yet again is another example.
If an SMA Video has helped you out please consider giving using "Patreon" to help support us. The videos take real time to create and pull us away from real work that pays our bills. CLICK HERE: / southmainauto
CHECK OUT OUR "SMA SWAG" STORE! Go on Teespring and get your very own SMA merch!
teespring.com/stores/the-sma-...
If you don't like Patreon feel free to use the "PayPal Me" link: www.paypal.me/SouthMainAuto
The South Main Auto Amazon Store:
www.amazon.com/shop/southmain...
AES Wave Automotive Diagnostic Tools: www.aeswave.com/cart.php?m=af...
Thank you for all the continuing support!
--Eric & Vanessa O.
Feel like sending some swag to SMA because you love the videos but don't know where to send it?
Just ship it here:
South Main Auto Repair
47 S. Main St
PO Box 471
Avoca, NY 14809
Disclaimer:
Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair 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 South Main Auto Repair, 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.

[@nickmayo2974]

Also, my 6 year old son loves your videos, I'm glad you keep it family friendly :) "Is that what you do at your work Daddy?" "Yep, sure is bud".

[@joeynobody1138]

😂

[@wyattoneable]

As basic as this seems it's still a great reminder of how to check for a voltage drop. There are guys like me who need to be reminded once in a while because we lack day to day experience. Thanks again for taking the time to teach.

[@throttletherapy9998]

Sooo true,me included

[@SmittySmithsonite]

I usually forget to do this because I'm in a hurry, especially when the problem is obvious like the terminals on this one. It should be the first thing I do, in addition to checking battery state of charge.

[@naquoashuey2794]

Spot on! I rarely do voltage drop. It’s a good test and CJDR recommends that over ohms testing. I generally load test and/or ohm test my circuits. I should do more voltage drop testing.

[@cohenjadiel9558]

I guess im asking randomly but does any of you know a way to log back into an instagram account? I somehow lost the account password. I would love any tricks you can give me.

[@chaimjude9800]

@Cohen Jadiel Instablaster =)

[@GeneralRELee]

Eric. O would make a awesome Auto Tech class instructor.

[@sully3010]

I was just thinking the same thing.

[@ianfahlman-morgan2081]

One of the best KZbin channels ever. I've been watching older videos back-to-back all afternoon 👍

[@FortyTwoAnswerToEverything]

Not "one of",..."The best" channel.

[@ianfahlman-morgan2081]

@@FortyTwoAnswerToEverything I stand corrected 😉

[@robertsise7898]

I concur.

[@BigDaddy_MRI]

Ian Fahlman-Morgan Me too. It’s like a very satisfying “This how you do it” drug. 😂😂😂😂

[@ianfahlman-morgan2081]

@@BigDaddy_MRI exactly! I diy all my volvo "projects" and Eric does a great job of confirming my suspicions when diagnosing

[@kyhomegarage3430]

Thank you Eric for all time and effort you put in your channel. Truly outstanding work. Cheers👍

[@CubasAutomotive]

You can definitely hear the difference in cranking after just cleaning the one terminal & cable.

[@SouthMainAuto]

Back to the basics :)

[@mykline1]

Can't believe who ever put the new batteries in didn't clean the connections. Rule number one. Was taught that back in 1969 when going through mechanics school. You have to have clean connections throughout electrical systems.

[@EvanT1995]

I'm in an automotive electrical fundamentals class in college right now and it's nice to see what we're learning being practiced on an actual vehicle! Thanks!!

[@Peugot905]

Watch scanner danner, he is the electrical GOD! I'm subscribed to his premium channel and it's packed with years worth of info.

[@jkbrown5496]

Why run down a 200 mV voltage drop? Because at a modest 60 amp draw from the alternator that's 12 watts of heat on that battery post. 0.2v doesn't sound like much until you apply the current. That's like a 1 amp bulb feeding heat right into the battery plates.

[@hethaerto1]

Very true. Also the heat exacerbates the corrosion development and wiring degradation.

[@HUBBABUBBADOOPYDOOP]

Be it a liquid, gas, photons or electrons- you can't find a leak until it's under pressure.

[@3347861]

Found a lot of problems over the years using voltage drop. Important to note that it will only show up when the circuit is under load. Once again, great video Eric. Thank you!

[@severomendez6889]

Thank you for making videos with electrical testing and repair. I started the automotive service program at my local community college and I am having difficulty understanding it and it frustrates me and makes me want to quit and go back to warehouse work. Watching your videos are extremely helpful, encouraging, and makes me feel at ease that I have a resource for extra information. Thank you, I really appreciate all of the videos!

[@moviejose3249]

Stay with it Severo it takes a good teacher sometimes and you may have to do your own digging on youtube to find one.

[@neverstoplearning382]

Do not give up. It used to be my weakest skill too. With a lot of effort and learning from pros like. Mr O, now I can diagnose with a lot more confidence and getting good results.

[@Ed-ip2sg]

This is twice this video has fixed my car. Great explanation of voltage drop.

[@chrisb3017]

Been a subscriber over a year, still can't believe you give this away. Thank you

[@eyesalooking]

Most thorough voltage drop test I have seen on internet that I have seen. I watched the video to the end. I learned a lot. Thanks.

[@rgebes222]

This is good timing, my college physics 2 class is all about electricity and circuit diagrams this semester. It's cool to learn all the theory but even better to see how it applies. These videos have actually helped quite a bit in class as well as fixing my old f150, which I think is pretty cool. Keep em comin!

[@zReignYT]

You're a great teacher. I just learned how to properly do a voltage drop test and what to look out for in your videos. And learned a whole lot more. My learning has been excelled from your channel. Amazing work. And amazing craftsmanship. Thank you!

[@johnboomer8468]

Thanks for sharing real voltage drop testing diagnosing. Your passion for fixing vehicles is awesome !

[@BigDaddy_MRI]

Just another outstanding video, Eric O. And, inside my head, the puzzle pieces make total sense. Thanks and please don’t stop. These videos are just like master mechanics classes. You da best!!!

[@procharger94]

Your channel is unbelievable. Thanks for all your effort and knowledge with these videos.

[@TheAdam212121]

I love your way of explaining your approach. Clear and to the point. I also appreciate you using a diagram. Great work! Subscribed and liked!

[@davidduran1877]

Currently learning this in class. Was having a hard time understanding voltage drop but after watching your video, I have a way better understanding of how the test works. Love your videos and keep up the good work.

[@rockiemountin7535]

Best auto diagnostics channel on KZbin Thanks Eric👍

[@SilverSergeant]

Nice job of explaining voltage drop and multimeter use....great job!! In addition, it shows how pretty simple preventative maintenance can prevent major issues......

[@SteveB647]

Great practical example of the effects of voltage drop. Thanks for taking the time to explain it so well.

[@renyn21]

These videos are a gold mine for the guy that cares about his car and would like to work on it himself. Thanks for making them Mr. O.

[@SmittySmithsonite]

Great demonstration here, Eric. A prime example of how voltage drop can affect any circuit. A high-amp draw circuit was the PERFECT example. What a difference in cranking RPM after ward! Could clearly hear the difference, even through the camera, across the internet, and through my speakers here. Was great to see the numbers vs. the cranking sound! 👍👍 My very first foray into this realm was with my aftermarket under-dash A/C system in my '72 El Camino, in the 110°F summer heat of Phoenix, AZ. The off/low/high switch I noticed was SUPER hot, when my finger got behind the Bakelite knob and touched the metal behind it. I could smell something burning, and the fans were real slow on high, too. Had a 5+ V drop across the switch! Wire connections were good, though - it needed a new switch (or, I could've disassembled it and cleaned inside it ... but it was all sloppy anyway). Installed the new one, and the fans blew stronger than ever. It's nice feeling 65° air when it's 114°F outside. 😁

[@Rockardo_]

I’m currently learning voltage drop at my training for my dealership and this is such a great way for me to see a real world scenario

[@nateottensman3040]

Please do more voltage drop and electrical videos! As someone who is trying to grasp electrical diagnosis I’ve been trying to soak up all knowledge I can including going to training seminars, AVI training videos etc. when you do the diagnostic videos it helps me understand what to do and what not to do so something does not go wrong. Thanks Eric!

[@robinsonsmotorcycleandauto3929]

Great video as always and a good reminder of checking voltage drop on any circuit thats not operating as designed.

[@ronbercan1000]

Great video. Thank you Eric. Measuring the temperature is a great ideal.

[@livewire6925]

Very good info for both the pros and DYI's because understanding the DC characteristics of a car circuits is usually not well known to most wrenches and can be the hardest symptom to chase down. Your explanation was very good. Dirty connections are man's worst enemy. Thanks again.

[@neverstoplearning382]

Thank you very much for taking the time and explain every single detail. Much appreciated. Master class, no question about it. Best regards.

[@tboneproductions2453]

Best video on voltage drop in action on the Internet. Thanks so much

[@viebien79]

Awesome video! Need to go out to the garage and do some of these tests. Thanks for the info!

[@dennismarble3591]

Another great job explaining voltage drop testing. Keep making these videos!

[@mikecont9742]

Really like these diagnosis and voltage drop/ parasitic draw videos. You have the best videos put there.....

[@cassiuspuckett8789]

Oooo!!! Nice lesson, Erick!!! I wouldn't have thought voltage drop from center of post to battery clamp would be that significant, but you just proved it is. Lesson learned is a clean battery post and clamp are a must to get proper voltage to the user item ( aka starter). Thanks for sharing Erick.....

[@colinpalmer5564]

Great practical video. Great understanding of ohms law..thank you for the pleasure that watching your videos brings. Keep on keeping on Eric..thanks

[@andrewkirwin6629]

Thanks for all your work Eric ,I’m learning so much from your vlogging

[@toddnelson2182]

Awesome explanation on voltage drop. Thanks as always.

[@scottstauffer1201]

I’m taking my first year heavy duty apprenticeship technical training and this video cleared up what they are trying to teach and this helped a lot with understanding voltage drop

[@alexandriabowe]

Eric O love your process using the basics, you slow down to go fast.

[@DependableAutoTruck]

these reminders are so good glad you took the time to show

[@hethaerto1]

My favorite video so far. I was not aware of this voltage drop method. Thanks!

[@Krillekris]

I love this channel. And you are good at putting out videos for us to learn. Thank you

[@372nww]

Very informative. Ive always been interested in how voltage drop works in a practical situation and your explanation was perfect

[@windycityben4850]

Great video man! Can’t forget those basics! I’ve only had to do a handful of voltage drop tests while I was at the dealer, but they saved my butt every time. Anyway another great video, look forward to your next. By the way you would make a great instructor.

[@jeremyproctor9671]

Thank you eric I like how you made it completely easy to understand !

[@erichagler7842]

this is a great video as many have stated this is one of those misunderstood test but, as you can see it is one of best tips and tricks that you should have in your box of knowledge ..... learn it live it . it could save your butt on many jobs load potential is a great bit of the problems on most all new cars or should i say the lack of load potential.....

[@iWatchVideosAtHome]

Hi Eric, I love watching your videos. I started working on cars for a living 7 months ago. You have the best car repair channel on KZbin by far, and I cannot imagine how much time it takes to edit and record everything you do on top of regular work. I was wondering if you have any videos repairing an exhaust leak on a GM truck with the 5.3/6.0/8.1 with broken manifold bolts? I have an 8.1 liter and the bolt that broke is on the driver's side closest to the firewall, of course.. I can't figure out how to search through your videos for some reason. Thanks

[@mikefedele4521]

I'm with you. I use the same technique as you do.... Numbers don't lie. "jumper cables" are an in the field thing done that too. I think you did an excellent job of breaking it down makes it understandable.

[@chrisbamford2196]

Thank you, this is the type of thing I try to tell people who want to know. You tell it very well. I'm going to use some of your expressions to improve my description.

[@ianmacgillivray2740]

That was one of my favourite SMA videos. You really packed a lot of good stuff in there for us diy'ers. Might have been kinda neat, to see the difference in temperatures on that battery connection (using your heat-seeking radar gun) lol!! Thanks.

[@workingraveyard]

All the customer had to do was replace the alternator too and he would of had the trifecta. Good example to diagnose a problem before throwing parts at it.

[@bradcampbell7253]

well at 250K miles.....battery and starter can be justified in replacement. but not as a diagnostic method.

[@febbral]

Excellent video on explaining voltage drop across to electrical points in circuit.

[@PCDoctorUSA]

Fantastic information. Definitely saving this episode.

[@nickmayo2974]

Good info and very well explained!

[@WBOS72]

Excellent video Eric. I love the diagnostic vids.

[@keangarvin2083]

GREAT informational video!!!

[@lonwillis783]

I love how you term electricity to plumbing terms! Good Job!

[@KennyMong]

What a great lesson! Thanks so much Eric!

[@gregeconomeier1476]

Great explanation of voltage drop. Now I feel the need to check my vehicles.

[@haywardsautomotive6156]

Nice voltage drop video. Understanding voltage drop, loaded circuit testing, etc is key to be efficient at diagnosing electrical issues. I wish we'd have learned voltage drop testing when I went to BOCES but didn't learn it until later and when I did it made diagnosing electrical issues so much easier and efficient. Understanding your test equipment & electrical fundamentals can't be overemphasized and like you said voltage drop at each connection may be small but when you combine the total drop it may become significant with multiple wire connections. Great video as usual and you are cranking out the videos...pretty impressive!!

[@Dreccomel193]

Nice... thank you for taking the time to make this video. 👍

[@JoesAutoElectric]

Nice brother! Toward the beginning of the video I caught a glimpse of that crust and thought it can't be that easy lol. This is a great explanation of the correct way to do voltage drop testing and you honestly have a fantastic ability to get your point across in a way that is easy to understand. Too many guys neglect this testing. Awesome bro!

[@docoski5518]

That’s what I’m talking about! Good job Mr. O!!

[@robertevans6481]

Wow 5 videos with bonus footage,,,,thanks Mr Eric...

[@danielwoodhouse1870]

Really good explanation thanks! Especially good for me as I am doing an apprenticeship and this was a good video to learn voltage drop from.

[@andrewcole9605]

You're the best and troubleshooting electrical electronic issue I feel like I was in class listening to my teacher terminology uses PD.

[@sting1111]

Excellent tutorial!

[@tomduncan1970]

Learned so much from this single video... Thanks Eric!

[@mikebidus7166]

Sir, You are an awesome teacher. No ifs and or buts. Just awesome.

[@SuperDave21]

Thank you Eric O., awesome video!! I can use this tech!

[@simplemangarage6678]

I've always been more prone to ohm testing a cable/connection vs volt drop. I would have been interested in seeing the resistance difference in before and after compared to your voltage drop test results. I do understand though that a circuit can show low resistance but not be capable of carrying a load or have voltage drop. Or both. Good video. Enjoy your veterans day weekend.

[@nemanjadzombic6101]

You should work out, then work your way in. I don't know other way to find VD, but this works every time. Hey Eric, I'm glad I finally joined the club. I wasn't able to folow your videos for two long years because of my poor English, but now when that improves I know all the effort I had put into language learning, now pays off. Ivan, Paul and You are my main seminars and training sources. Although I'm professional I would be nowhere without you guys and have still much to learn. Greetings from Serbia :)

[@michaelroblin1957]

Very informative video Eric!

[@1231234abcab]

Again, I really enjoy your diagnosis videos 👌

[@rsanchez5676]

Very well explained. Love voltage drop for parasitic draw testing across fuses.

[@baxrok2.]

Outstanding content here Eric. Loved it. I hope people appreciate the diagnostic gold in this video. Thanks Dr. O! BTW, on the Vantage Pro, as long as the voltage range box is highlighted, there is no need to press the Yes button, just use the up down buttons to change the range. Saves a bit of time.

[@SouthMainAuto]

Thanks for the free tip friday :)

[@NoWr2Run]

It's DAMN SAD that somebody put new batteries & left those terminals like that. JUST PLAIN LAZY IF YOU ASK ME, THANKS ERIC, VERY EDUCATIONAL AS ALWAYS. Hey you do have a remote starter, NICE, I have one from the 80"s, very nice to have, you don't have to keep running in & out to start the vehicle. As I said in an earlier vid. YOUR'E LIKE BATMAN WITH ALL THOSE WONDERFUL TOY'S.

[@billsmith2212]

Not lazy , STUPID IDIOT !

[@Lake_Lover]

Eric - Wonderful video! I learned this a long time ago when I was in the Navy in Electronics classes. Folks - understanding voltage drops is essential to your basic knowledge in my opinion. I had this very thing happen to me Memorial Day at the lake. Went to get the truck to recover the boat and it wouldn't start. Mt voltage drop was actually the ground connection on the driver's side head. Removed the bolt put it back in - whola truck cranks and starts. I used a Fluke 77 multimeter to troubleshoot. Having that meter and voltage drop knowledge has saved me lots of money and helped me fix lots of problems. Stay safe out there !

[@Viper81766]

Amen brother :-)

[@Viper81766]

And thank you for your service 😀

[@Lake_Lover]

@@Viper81766 thank you Robert.

[@Viper81766]

@@Lake_Lover In 2013-14 I took two semesters at a local community college in automotive electrical and engine performance . Our teacher was a 69 year old gentlemen who served 22 years in the Air Force and 20 more years teaching electrical classes . Best teacher I had in all my years . Sadly most younger men could care less about learning this field . Very challenging and rewarding if we apply our selves to it .

[@Lake_Lover]

@@Viper81766 Wonderful ! Like I mentioned earlier I took several electronic courses in the Navy graduating an working on top secret avionics. From there, I got bit by the computer bug back in the late 80's and early 90's. For the last 26 plus years I've been doing IT work - now at a community college in east central Illinois. My father/brother and I are all mechanically inclined too. I'm very intrigued by the marrying of auto mechanics and computers in cars managing engine and other car functions. I've been subscribed to Eric's channel for a while now having watched every video he's produced. The first being the AC repair on a 02' Taurus. The first video's that I watched that had electrical/electronic troubleshooting in them really had me thinking the Eric had been in the service and went through electronic school. About the time I was going to ask him during a "what's up Wednesday" someone else had already asked and he has not been in the service. His approach and reasoning skills are so much like mine it's scary ! LOL.

[@spelunkerd]

What surprised me most about relearning ohm's law was the hyperbolic shape of the current/resistance curve for a fixed voltage. Effectively that means a nearly vertical downward slope for low resistance circuits that rely on high current. So, those high current circuits suffer a HUGE compromise of power delivery from even an ohm or two of corrosion. Minor circuits don't even notice a little extra corrosion, they work on the flat part of the graph where you need a big change in resistance to have any effect on power delivery.

[@russlehman2070]

Resistance is critical for automotive circuits. With just 12 volts (or 14 or so with engine running), you need 10 times as much current for a given amount of power as you would for 120 volt household electricity. That means anything that draws a significant amount of power has low resistance, and will only work if the wiring supplying it has very low resistance.

[@klystron1]

Good educational video, thanks Eric.

[@1977jelliott]

Top vid! Voltage drop tests are sooooooo important.

[@4ikemir]

Just want to say thank you for sharing your knowledge. God bless you

[@actionsmitty]

Free tip Tuesday on a Sunday. I always spray the battery terminals of all my vehicles, atv’s, snowmobiles etc with fluid film when they are new. I live deep in the rust belt and it prevents corrosion from forming. I also spray all ground connections on the vehicle as well. Fluid film creeps into the connection and the cable strands and does a great job preventing problems. When working on someone else’s vehicle I make sure the connections are surgically clean then spray them.

[@brandonj9974]

Great diagnostic video. You used a solid technique for explaining the tests and how to perform them. Which snap on scanner did you use with graphing functionality...works great. Thank you

[@coycarlson4979]

All the stuff South Main Auto demonstrates / teaches is GREAT STUFF 👍😊 YOU have many , many years of PROVEN EXPERIENCE and vehicle repair knowledge and when I watch you make repairs and you say - if I can do it - you can do it - I'm STOKED 😊 Again - GREAT INSTRUCTION , I learn something from every video you make - MANY , MANY THANKS and , no doubt , if I lived near you - I would surely bring my vehicles to your shop for repair and ABSOLUTELY REST ASSURED - knowing you would repair it properly. ✌️✌️✌️

[@billmcdonald1296]

Great video. Super work.

[@johndemoss2969]

I am retired and 71 years old. I'm teaching myself to do Auto Electrical. I have watched a lot of Electrical Videos on KZbin. But Eric O is the best teacher that I have seen on here. Learning Voltage Drop is so important. What a great channel to watch !!

[@fredberfal1246]

Excellent Eric , as always !

[@reinhardeder1829]

I like the way you explain voltage drop in kind a pressure ,....very good

[@donburky6777]

As a new subscriber and a A.S.E. diesel d&r certified tech. I love the diesel tips, because even I forget the simple stuff. At the beginning my first diagnosis was a bad ground, thinking that it was a rusty frame. I've seen worse terminals on big trucks, but wow that was a lot of crud.

[@leightonwhisenhunt13]

I would love your input, my ex wife has a 2002 Jeep Liberty with a 3.7, on cold starts you have to crank it about 2-3 times before it eventually starts. I replaced the fuelpump, has great spark and fuel pressure. When it's warm, it starts right up. I've worked on cars all my life and I can't seem to figure this out. Any help is appreciated. Thank you. You are hands down THE BEST mechanic I've seen so far on KZbin.

[@xxrodneyxx]

Awesome video on difference of potential!

[@samsquires2877]

Fantastic video on explaining this.

[@erikkirby4534]

Great video as always Mr. O! That dodge makes me remember the time i rebuilt one.... Man the head is heavy!!!! So is the crankshaft!!!!

[@maureenpye9252]

U should be teaching your way of explaining is the best I have seen í am an older tech in nz re training to keep up b the influence of having a family support you is great to see keep on trucking thanks for another awesome video

[@777gearhead]

that was a fantastic video. lots of great information.