Diagnosis and Understanding- Voltage Drop

Even most advanced DIY's and troubleshooters are not familiar with Voltage Drop Testing. This video shows a real life example of how lack of knowledge of this important skill can lead to misdiagnosis!
Further, voltage drop is illustrated in an easy to follow manner so you will understand voltage drop for the rest of your life without having to look up how to do the testing or when it might apply.
Other videos with voltage drop test or relevant material:
Fuel pump testing: • Low Fuel Pressure,Lean...
Diagnosis and testing of relays: • Relays- Understanding,...
Also for many electrical testing tutorials and videos see my friend Terry's channel Stuzman52 / stuzman52

[@1q2w3e922]

I have been an electrician for 40 yrs, a US navy trained aircraft electronic tech for 4 yrs and have taught the subject as an NCCER certified instructor. I have never thought about testing for voltage drop very much under load. My hat off to you young man. You can always learn new things. Excellent video

[@del9936]

oh dear, if i was a US navy pilot i would be shaking in my boots going to fly if thats how the US train electronic aircraft techs and they dont understand voltage drop ,very frightening.

[@1q2w3e922]

@@del9936 everone that knows ohms law understands voltage drop. VD under a load, as he explained, is a totally different situation. But in aircraft avionics a tech understands the system and its operation as a whole and what each black box, computer, gyro, sensor, accelerometer or whatever does. So when the pilot turns in a "gripe" 99 % of the time I knew exactly which unit to replace. The other 1% of the time is why we had company tech reps to really dig into the problem following complicated schematics and scratching his head.

[@jewelsmartin4861]

@@del9936 Ujjain

[@thehumbledabbler]

@@del9936 he dfnt say he dont understand voltage drop. He ddnt consider this particular method. There's no way he'd be teaching our military if he was incompetent. Have some respect would u

[@josephfdunphymba3241]

MECP certified here, and i thought this was an extremely clear presentation

[@moog2961]

The best tool in anyone's toolbox is the brain. It doesn't cost a penny to upgrade it, just a little time and help from other people. Thanks Mat.

[@jpattoncook]

I’ve sat through years of college courses, math, chemistry, physics, etc. Your teaching is as good as ANY college professor, any professional seminar or instruction that I have ever had. Thank you.

[@SchrodingersBox]

Thanks man! We all should do our best to identify and use our gifts and talents to help others!

[@princeclive1913]

I really don't understand voltage drop until today thanks for your teaching and your explanation..

[@murhafsukkar9555]

That’s exactly why his videos are my favorite. His methodology is broad and deep; reminds me of grad school

[@mathematicatft6149]

The water comparison is pretty intuitive, even for those without a background in math and science. For me, I just smiled because it reminded me of learning about Gauss' Law, Maxwell's equations, and the concept of flux. For my fellow nerds here, the continuity equation is a really nice bit of mathematics that is very applicable to both fluid dynamics and electromagnetism. Edit: I'd like to add too, that my first undergraduate physics professor prefaced our Gauss' law lecture with some similar intuition regarding fluid flow. It's a really good direction to go when explaining this stuff to others

[@Impedancenetwork]

You have got to be kidding me.

[@labradormcgraw]

This guy never ceases to amaze. He has a true gift for enlightenment. This video is actually a great complement to a much more recent series: 'Basic Electrical for Beginners'.

[@WOODOGS]

I have studied electrical concepts and theory for twenty years. Your video is the best explanation, image, and approach to this mysterious subject that I have always wondered about. Obviously, you have wisdom about your craft, and I appreciate you sharing that with KZbin. Thank you again for your time.

[@SchrodingersBox]

What a nice comment! Thanks!

[@director2345]

Excellent explanation of 'voltage drop'....You showed the hands-on, as well as the theory under different scenarios....This is what proper teaching and learning is all about.....Your presentation is done perfectly, and allows us to grasp the details of what some of us thought we knew over the years...Keep up the good work.

[@hanyemara9572]

Been a diesel mechanic for 6 years first time to understand that continuity and resistance test aren’t good enough to decide that the circuit is good or bad. And you will never know that you have a hole in the water hose and the hose is bad until you apply water to it and same goes for wiring. You’re freaking awesome thanks a ton

[@SchrodingersBox]

glad to hear! yes it was also years before I was able to put it together as well. totally makes sense once you get it though! and you never forget it either and it makes learning new concepts far easier.

[@electronmarkboggess63]

I was a mechanic in the Army for 12 years and that's the one thing all the troubleshooting procedures I've ever followed didn't have you do was voltage drop testing.They would instead have you "ohm out the wire" to look for resistance lol..They sent a bunch of us to an advance electrical course at a local collage and that's where I was introduced to voltage drop testing and many other very good procedures that our training and manuals didn't teach.. great video!!

[@hwingerrr5680]

You can make a milliohm meter if you have a power supply that you can set for 1A constant current; just run the current through the wire and then use your DVM and measure millivolts on the ends. If it reads 5 mV, it would correspond to 5 milliohms. No regular DMM resistance mode can resolve that because they use tiny currents. I've done this method to characterize how good a set of jumper cables are, works really well. If you do this a lot, you can buy Kelvin test leads that have four wire connections to alligator clips that have isolated prongs on each side, to allow a four wire measurement, where the current passes through one set of wires, and the measurement is made on the second pair of wires.

[@allorobiekwe5080]

I was on the verge of changing my starter motor before I saw this video. I had the same problem and it's fixed now. Thanks so much for your very helpful video.

[@labradormcgraw2409]

This guy is brilliant! Just can't understand why he hasn't got more subs. He makes things so easy to understand - the hallmark of a great teacher. Love the format; love the visuals; love the commentary. This guy knows how it's really done.

[@digemsmacks5690]

Hotdogs.. needs to use hotdogs for electricity demonstrations and those subs would rise for sure. Its a shame but true. This information would have to have been paid for in the past

[@SchrodingersBox]

An unusual idea but probably worth a try and I have a feeling you will be contributing more such ideas in the future for some reason hahaha. Glad you found the channel.

[@leondavis8062]

This is still the best explanation video about voltage drop I've seen after years and still is.

[@Curtiss1965]

This is awesome. As a diy'er-wannabe, I learned more in 33 mins from this guy than several hours of watching other videoes. Well done sir!

[@joshuabastion995]

Absolutely spot on statement.. Fantastic nii1jmmjbuuùùiuohkjhhhjķkiķķķkkkķjjkkklķķ0

[@anthonycruz3568]

This is by far the best explanation that I've seen mad respect for this man that took the time to make this video

[@PineHollowAutoDiagnostics]

Great video, Matt! Another great application of voltage-drop testing that I discovered yesterday: locating breaks (opens) in your rear window defogger grid! Instead of poking around with an ohmmeter, just turn the defogger on, clip the ground lead to the ground cable on the grid, and use the positive lead to probe each line in the grid in the middle of the window. If you read 6V (~half of B+), then that line is carrying current OK. If the reading is B+, there is no current on that line, and the break is DOWNSTREAM of the + lead. If the reading is close to 0V, then the break is UPSTREAM. It literally took seconds to locate three separate breaks using the voltage drop test, after 15 minutes of frustration with the ohmmeter :)

[@SchrodingersBox]

Never thought of that. I have always done it using continuity test to fine the open.

[@davenichols8713]

motoYam82 Holy cow that is so much easier!

[@SchrodingersBox]

Dave Nichols Agreed. Great tip Moto. Man I love the comments section- I learn more from them than any other source on earth lol!!!

[@petrocksgarage]

Schrodingers Box, like in your video, a continuity & ohms tests is almost useless. There could be a damaged wire with only a single strand connecting the two halves and a continuity test will say the wire is OK when in fact it’s not. It has excessive resistance because that single strand can’t carry all the voltage and current in the system. If you think about it there are only three ways a circuit can fail (open, short & excessive resistance). A series of voltage checks can tell you which type of failure occurred and pinpoint it’s location in the circuit pretty quickly. Using a binary search makes finding the fault even faster.

[@aleksandrzinkevics1253]

Pine Hollow Auto Diagnostics hi Иван! Any video about it for people who is not so clever as u? Please

[@thomvogan3397]

You are by far the best teacher on the internet. I live on a small pension so anytime I can fix something myself it's a big help. I've been having intermittent problems with dim or no headlights along with slow wipers. Thanks to this I now know I probably have a bad wire or connection on a circuit that controls both. I see this video is dated 2015, hope you're still putting them out. Thank you

[@SchrodingersBox]

Wow, thanks! Very glad to be of help!

[@keiths8700]

For someone who claims they are terrible with electrics, I have to say that was the best explanation on youtube of voltage drop.

[@SchrodingersBox]

Haha thanks. I used to be terrible with electrical. Like really bad. But shortly before this video I taught myself how to do it and now electrical is one of my strongest assets by far. But there was definitely a time that was not the case!!!

[@keiths8700]

@@SchrodingersBox Yes, I am the same way. Thank you for a great video.

[@staind288]

I appreciate your time you took to make this video. It really helped me understand how to diagnose and measure voltage drop.

[@davidperrone2992]

Dude, very very good video. Way better than a lot of the other videos I've watched on KZbin. Thank you.

[@malibugrif]

This is brilliant! Matt not only explains this concept well, but he gives an elegant demonstration of how to diagnosis (and find) this rather tricky electrical gremlin. You can use this same concept in home wiring ... really any electrical circuit.

[@SchrodingersBox]

Thank you!!

[@Carlostype]

Agreed, voltage drop testing and understanding is essential with diagnostics, I've spent hours watching various KZbin tutorials until it clicked and hopefully never forgotten. A good battery voltage drop test with just your dvom- as you crank just prior to start you see the measured drop across the the posts- below 9v it's weak for example, good post Mat

[@SchrodingersBox]

The battery test cannot differentiate voltage drop from battery drain though. If you have 9V between the terminals and no voltage drop at the starter, you have battery drain. If you have 9V at the battery and 7 volt at the starter, you have 2 problems.

[@davenichols8713]

Schrodingers Box Excellent. You found what I was trying to think of after reading your comment Typey1. So, if you wish, test the battery directly during starting, and again on it's wires to the starter as a 2nd test.

[@SchrodingersBox]

Dave Nichols Exactly. Subtract those readings and that will be the voltage drop in the wiring.

[@davenichols8713]

Schrodingers Box I was craving this channels comments even though I didn't have time to watch the show at the moment, lol.

[@SchrodingersBox]

Dave Nichols Lol, sometimes the comments are better than the video!!

[@darkwolf06vheb5]

Those 35 thumbs down are parts changers. Awesome video!

[@SchrodingersBox]

correct! But also it indicates I am doing a good job of deterring them from the channel though since parts changers make up 98% of the population yet represent less than 2% of my viewership.

[@GlycerinZ]

The issue I have with parts changing is I like to know exactly what part failed, and then if possible, why it failed. Plus parts changing costs more money and I like to use my brain to figure out problems.

[@inthemidwinter]

When your boss overrides and says just get a starter coming. Instead of allowing you to make absolutely sure... -___-

[@Accarvd]

now 102... I had to review this video :D

[@davidthomas6949]

@@Accarvd just to upddate... still 102. This video really does go DEEP in physics, without the calculations.

[@chrishemphill3684]

Thank you!! I have been trying to wrap my head around voltage drop and you made it so much more clear

[@web5271]

Damn. 33 minutes!!!? Maybe the best 33 minute youtube video I've seen in a long time. I've spent 2 days doing exactly what you did, replacing starter, relay, nuetral safety switch, checking ignition switch, wailing and knashing of teeth.

[@jamesmancine8350]

Excellent video. I had a neighbor with a starter issue on their matrix. After checking the battery, I had my neighbor attempt to start the engine while I stood by. I checked for voltage drop, zero voltage drop. I checked for voltage at the starter terminals, there was voltage, I tapped on the solenoid, asked her to turn the key, it started right up. It turned out it was a stuck solenoid. It saved them a wallet full of diagnostic fees, all they needed was a solenoid instead of an entire starter, they were happy.

[@patriciacollado2673]

this guy is a professor!! 5 stars from me. thank you boss!!!

[@OzzySepulveda]

This is golden! Going to my save this to a playlist.

[@jalopyjoe3069]

Great content my friend. A great example of this is a electric fuel pump in the tank. The circuit may start with 13.8v, but with 20ft old, small wire. We have 11.25@ the pump. The cure, rewire the pump with adequate size wire, and a new relay. Now I have 13.65v, giving me 25% more flow.

[@SchrodingersBox]

Indeed that is a classic example that I have seen happen several times. And not just fuel pump- headlights, tail lights, starter, etc. It is critical that a good diagnostician understands voltage drop!!

[@kyclay58]

Thank you!!! Awesome, easy to understand, video. I now understand voltage drop better than I ever have. I will now tackle the no start situation on my motorcycle with confidence.

[@vincentmedina1092]

More of a visual learner. Using your videos to help me pass my ASE test’s but also understand Electrical 👌🏽. Excellent video.

[@SchrodingersBox]

If you want to really understand electrical visit my website at www.schrodingersboxqm.com

[@practobootsier852]

You are a brilliant teacher. Really great hands-on explanation!

[@DarrenWoolford]

Great Video, really helped me understand the theory behind Voltage Drops. Been a Technician for 12 years, never had the "capped" off explanation before. Thanks again, and I have subscribed, so look forward to more!

[@KevinCoop1]

Thank you very much! I'm an electrical design engineer for construction. I have done thousands of voltage drop calculations in my life. I recently helped my son diagnose a bad starter. The bench test proved the bad starter. I would have been in trouble and not thought of checking the way you did if the starter spun up on the bench. Again thank you for the video! Oh, My other son has a diesel lawn tractor having starter issues. I will add this to be checked next time it will not start! Thank you so much! Respectfully, Kevin

[@sukeshford2013]

this practice voltage drop 100 percentage correct ..this very help full for ford technician

[@dreamer2355]

Great video. I wish more technicians in the field knew about voltage drop testing :/ I also have those loadpro leads :)

[@pas3463]

As a software engineer sitting 5 days per week at a desk, nothing is more relaxing than being active in my garage. I love your show and i am very impressed by your "teaching" skills. Best regards from the Netherlands.

[@kenbell2745]

So simple, so accurate. To have some one tell Me that they put on multiple electrical components to get a good one.........I always tell them they happen to fix the real problem not even knowing it or admitting it. It is a real time saver.

[@ozzstars_cars]

Couldn't be explained any more clearly. Excellent

[@mykofreder1682]

It comes down to the same argument he made when the motor turned out of the car with jumper cables for the same reason, it turns without a load but does not have the power to turn under load. A motor with that problem probably has bad connections, insulation, wire within the winding that is not 100% open. The same can be true for a wire, the current of an ohm meter is very load and might not show bad wire or connections that are current dependent. This can also be intermittent if it need the heating of current flow through the resistance to fail, I had an ignition coil like that, it ran fine cool, but once heated up it failed and I lost a cylinder. Good diagnosis and if you know what you are doing gives you another mode a odd failures, this is an odd failure and probably does not happen often when a starter appear dead.

[@JoseAguilar-xc3dw]

Thanks Matt

[@jakeford1570]

I'm blown away. Thank you so much for giving me something I can use the rest of my life. I was watching this like a 13 year old girl watches keeping up with the kardashians.

[@norlure]

Who are the kardashians ?, Are they related to Klignon...?LOL

[@atomicdmt8763]

Covidashians

[@yusufronco]

I'm really glad that channels like this exist. Being able to work on your own vehicle is very freeing and stress relieving, knowing that your life isn't at the mercy of under-built/ disposable modern cars.

[@Inevective]

Holy crap! I have a basic (somewhat cheap) multimeter and it only has the main test leads. I wanted it to have the alligator clips as an option if needed. I was almost considering wiring additional leads with alligator clips on the end. I NEVER considered just attaching the alligator clips directly to my existing leads! Completely overlooked that option! I feel like an idiot! You my man are a genius! I've already subscribed. All of your content is amazing. I recently stumbled onto your channel doing research. I just replaced the timing cover gasket on my 03 Impala and after reassembly, it would crank but not fire. In the process of learning your FASTTEC method right now! Please keep doing what you're doing, because you're (like you say) one of the only few that actually takes the time to figure it out and understand it. But more importantly, you actually share your knowledge as one of those people! You rock bro! Dig your set up too!

[@SchrodingersBox]

Haha thanks for the great comment. glad you found us!!

[@ibrahimalnajjar277]

am watching electricity videos for 10 years but this guy is really the best explanation that i have never seen before thankssssss

[@michaela.660]

Volt drop 501- When you have done all this and are experiencing a slow cranking starter or dim 13 watt light bulb. Remember that each contact point regardless of size or type (unless soldered) has a volt drop value of .1 (point 1 or 1/10 th) of a volt. This means, say for example, your wiring diagram shows the blower circuit on high speed ( not being feed through the blower resister) has 15 potential bad contact points in the whole circuit, the total VD VALUE ADD UP TO 1.5 V. TYPICALLY UN THOUGHT OF CONTACT POINTS ARE : Brushes, Rheostats, Mechanical contacts internal of a switch, Grounds to body, Grounds back to battery from body. I use this test to determine the overall health of a circuit (after accounting for total contact points). Then if it does not add up +or- 3/10v go to point to point volt drop testing, then to ohming point to point. 20 MINUTES OF VOLT DROP TESTING WILL SAVE YOU HOURS OF GRIEF FOR ME IT'S THE FIRST STEP.

[@davidthomas6949]

Can you explain further maybe make a video about how you do all of this in 20 mins :P considering the number of positioning of ground points in the car, Id say this is a week long job. Also, why do unsoldered contact points translate to VD of 0.1V? Id think thats a generalization, and can be eliminated with something like DiElectric Grease, or am I missing the point?

[@davidthomas6949]

ALSO #2 how d we locate the damn potentiometer/rheostat or the "Mechanical contacts internal of a switch" in 20 mins and service them?

[@jmyers224]

Your explanations helped me to conceptualize what's actually going on in a way that will carry over into other situations. Best half hour on you tube, thank you so much!

[@williamfaubion1082]

I'm in school right now to be an aircraft mechanic and we were learning about voltage drop, and how to diagnose a problem. I was having a issue with it until I watched your video. So thank you for explaining this so well. Your example will help me in the future I'm sure of it.

[@rbarr1200]

Auto parts stores can be brutal. I actually feel pain when I hear certain people buying parts. I once heard a guy asking for pricing on a MAF sensor and said he already replaced fuel pump and filter and injectors and that he still had a low power problem AND THE GUY WORKING THERE says..... I would bet it is the MAF. I almost threw up.

[@davenichols8713]

Ricardo Barron I watch parts sellers very carefully. All the ones I work around avoid confirming any customer diagnosis. I'd throw up in my mouth too.

[@SchrodingersBox]

Couldn't agree more. What infuriates more than anything though is when parts places actually take electrical parts back. The idiots don't understand that any number of issues can cause an electrical part to fail when it is connected and then they take back a defective part and resell it, causing people who actually diagnosed correctly to spin circles when the new part also failed.

[@davenichols8713]

Schrodingers Box I've had a similar effect from a new, improperly calibrated part (OEM MAF). When I condemned a brand new part and replaced it on a guarantee it was a rather proud moment provided by my association with you.

[@FishFind3000]

Schrodingers Box my hvac suppliers will NOT take back anything that has been hookup.

[@hammershigh]

Sorry, I have to correct you regarding 2 things :) 1. Ohms law is a law that concers DC voltage. So if you measure zero ohm in a wire, then there IS zero ohm independent of current. Also called a linear dependancy. So the only physical explanation to your experiment, is the special situation, where the wire sometimes is leading, sometimes not ( a momentarily malfunction of the wire). This error can be provoked by wigling the wire. And the "break" can occure anywhere on the wire and be caused by repeatedly movements over time of the wire. 2. You forgot to take into acount potential testing wire problems. best regards

[@tonyfremont]

I think his point was that the ohm reading can be misleading. You are technically correct, but take a cable with a bunch of broken conductors, yet one is still good. It will measure 0 ohms, yet when the current starts flowing, that single thread glows red hot and resistance shoots up on it. The ohm meter flows a miniscule current, so the wire resistance stays low. I would like to know what exactly was going on inside that cable to behave that way.

[@ericscaillet2232]

@@tonyfremont broken strands, internal oxidation, previously overheated, chemical contamination etc.

[@coburn_karma]

The best explanation of Voltage Drop done thoroughly. Save your reputation and money as an auto technician.

[@antonioponce6544]

Your video is most instructive. I've been watching a few other auto mechanics show how to use voltage drop and explained it sort of but I just couldn't quite get it. You make it perfectly clear, even for a dummy like me, and now I can use it as a tool when needed. Thanks.

[@petrocksgarage]

Great video. As the old saying goes: Mechanics go to the part. Electricians go to the wires. I completely agree that continuity tests & ohms checks are useless. Voltage testing is the way to go. But I think your continuity test was inaccurate. To do a proper continuity or ohm test you need to isolate the component under test (CUT) from the rest of the circuit. An ohm-meter does it’s job by sending a small/constant amount of voltage & amps through one lead and applies a ground to the other. It then measures the voltage drop between the leads to figure out the ohms reading (via Ohms Law). Since, like water, electricity takes the path of least resistance, if the CUT is still connected to the circuit there is no way for you to know which direction through the circuit the current from the meter is flowing. So there is no way to know which side of the circuit you are testing (positive vs negative) or which component in the circuit you were testing. The current from the meter is going to flow in which ever direction has the least amount of resistance, and the meter will display that resistance. I bet if you disconnected the positive cable completely from the battery & starter you would get a much different ohms reading.

[@edwaggonersr.7446]

+Pet Rock's Garage "I bet if you disconnected the positive cable completely from the battery & starter you would get a much different ohms reading." I don't think you are correct.

[@petrocksgarage]

+Ed Waggoner Sr. (Papatch) Could you elaborate on why you think so?

[@edwaggonersr.7446]

Pet Rock's Garage The ohms meter pushes so little current that one could get the same reading if only two or three strands of the braided wire remained in tact.

[@petrocksgarage]

+Ed Waggoner Sr. (Papatch), yes, but my statement was that he would get a different ohms reading after isolating the battery cable from the rest of the circuit. With the battery cable connected to the rest of the circuit there is no telling what path the current from the meter is taking and therefor no telling what part of the circuit the ohms reading is actually measuring. If he wanted to measure the resistance of the battery cable then he needed to isolate the cable.

[@edwaggonersr.7446]

Pet Rock's Garage Oops. You are correct. Yet, an ohms test would not tell you if the cable could carry a heavy load; so why bother?

[@jptrainor]

Condensed version: You need to measure a very low resistance value to accurately test the conductor due to the high current nature of the application. The difference between very very low, and merely very low, resistance will matter in this case. A simple two wire ohm meter cannot accurately measure very low resistance values. Instead, pass a current through the conductor and use your cheap meter to measure the voltage drop, apply ohms law to get the conductor resistance, or interpret the voltage drop directly, as required. p.s. In regards to the two wire meter's inability to accurately measure low resistance values - it's a case of the observer affecting the observed. Ironically, this appears on Schrodinger's Box.

[@MMGJ10]

And this is the video I should've watched before changing out my starter. I did things exactly how you first did and ruled (or so I thought) everything out except the starter. Tomorrow I'll be better armed to figure this out. Thanks for the concise explanation of voltage drop. Great video

[@jawojnicki]

Matt, you are the BEST automotive diagnostics teacher on you tube - bar none! Thanks for all of your help. Here's a ? - I have a 1998 Chrysler TandC with a 41TE auto transaxle. Fluid level is normal and not contaminated. Randomly, the trans will fail to "drop into" any forward gears. Shifter moves freely, but in any forward gear, you don't feel that "clunk" you get when the gears actually engage. This goes away when revving the engine up to about 3K RPM. Once engaged, car drives normally - therefore, I think it CAN NOT possible be a mechanical issue inside the trans. I HIGHLY suspect (because other electrical things in the car randomly fail and "heal") there is an issue with the TCM or the PCM, but I don't own a scan tool. I checked your vids on your site and don't find any that explain TCM or PCM diagnosis. Do you have one or could you make one PLEASE? I dont' trust any other YT personality with something this confusing. Keep the great vids coming.

[@raycook1503]

This is the best electrical video I have seen. It makes you aware to explore all avenues before a part replacement. It makes me think differently now.

[@SchrodingersBox]

Glad you appreciate it!!!

[@pablovidales8489]

I never stop watching you videos,always learn something new every minute no matter how long it is.thank you 🙏

[@SchrodingersBox]

You are so welcome

[@raullcalzadilla3541]

Fantastic, I understood everything, for the first time, even having watched other videos. You are a gifted teacher. Thank you so much.

[@SchrodingersBox]

Oh wow thanks!! Made my day!!

[@Joserocha-wm9de]

This is a 7 yr old video but it's probably the best video on YT explanation about voltage drop test ⭐⭐⭐⭐⭐👌 Tyvm sir , i learned something new with something old 😂 👏👏👏👌

[@SchrodingersBox]

Glad you liked it!

[@Joserocha-wm9de]

@@SchrodingersBox i loved the entire video explanation , but i have a question : In that case the positive cable was bad but that can also happen with ground cable right ? Like get corroded and get a huge amount of resistance ? Thx

[@SchrodingersBox]

Absolutely it can!!! I have found bad grounds or bad ground cables many times.

[@Joserocha-wm9de]

@@SchrodingersBox Thats what i was thinking , tyvm

[@movingupautodiagnostics8645]

Man I don't undestand why anyone would dislike this video... Thanks for sharing this info, to me it's very powerful. I've tried it in the past but now I fully understand what voltage drop is. Great video Matt, hope everything is ok.

[@SchrodingersBox]

Thanks man. I've come to find most people dislike it because they still don't understand it. I can only do so much I guess.

[@basdoesthis]

What a great video 9 years later... learned alot from this

[@gilberthale7777]

Checking for voltage drop is a step I take when conventional diagnostic techniques do not tease out the cause of an electrical problem. It is sure fire, but seen as being mysterious by most folks I come across - if they even ever heard of it. I see it as straightforward, sensible, it is a "dynamic resistance" or "effective resistance under load" kind of testing, where some problems only appear when there is current actually flowing (or trying to flow). It is hard to get to the point without all the preliminary explanation, just like it takes a while to go through more routine diagnostic steps before doing a voltage drop test on the various connections in a circuit. The concept and realities with voltage drop analysis were well presented, and the time taken to watch and listen to this video is worth the time. Heck, it was worth the time for me, although I already knew about voltage drop testing, just a a refresher - and to see that there are some other folks who understand it well enough to use it in a diagnostic routine. Very cool...

[@SchrodingersBox]

Thanks for the great feedback!!

[@RickyPisano]

Listen to what Matt says between 12:00 and 12:30. It's the reason this channel ROCKS!! It's the difference between this channel and 98% of every other automotive video I've ever watched. And I've watched A LOT of them.... trust me. Outstanding video as usual Matt!!

[@SchrodingersBox]

Thanks again!!

[@RickyPisano]

If you want to understand why something isn't working in your engine or car electronics and how to fix it WITH LOGIC you're in the right place. If you just want to know how to replace parts on your engine or car electronics..... move on. This channel teaches the WHY and the HOW. Just a fantastic channel for DIYers. My personal favorite.

[@SchrodingersBox]

Well said my friend!! Perfect synopsis!!

[@maciejf.]

I've just fixed my ABS issue recently caused by a voltage drop on an oxidized fuse holder. The symptoms were completelly misleading, as the problem only appeared when under load. It took me 2 years to understand, diagnose and fix, by cleaning the contacts, at zero cost. Watching the vid now afterwards is eye opening to say the least. :)

[@caiocesar4136]

I'm a Brazilian mechanic and it's hard to find classes like yours around here. thank you very much for sharing your knowledge, your classes help me a lot to improve my service.

[@SchrodingersBox]

Glad to help!!

[@coolbluelights]

I've been using DMMs and working with electronics/electricity as a hobby for over 20 years. if you had told me yesterday that you could measure a voltage by putting both probes on the positive side of a circuit I would have laughed in your face. Wow. This knowledge is a total game changer!

[@SchrodingersBox]

I used to think the same!!! yes the information from voltage drop on one side of a circuit is one of the most powerful diagnostic abilities you can have. And few people understand it- very few. Congratulations!

[@kman-mi7su]

"The gift that keeps on giving" I saw this video three years ago when you posted it. I'm using it once again to fix an issue on my 1988 Ford F250 7.3 diesel pickup and also used it on my teenage daughter's 2004 Toyota Camry, my girlfriend's 2012 Kia Sedona, my neighbor's 1985 Chevy pickup, and even a vehicle at work (shhhhh I'm not supposed to be doing that!). Thanks again, and again, and again, and again, and, well ya know!

[@SchrodingersBox]

Lol often if I re-watch a video I made years ago I cringe at how horrible my electrical knowledge was but this one still holds water!!

[@kirstenspencer3630]

Yes, voltage drop is critical in quick diagnosis, was taught this by Murry " Mac " Fernandez. Thank you " Mac " made my life sooo easy !

[@mechtech104]

The first 10 minutes of this video accurately described my original process to my starter. Only after I bought a battery and test my starter did I know it must be the wires. Thank you for this!

[@davidgald3072]

Great stuff, was doubting the direction when I first saw the beginning of the video and then I realized I was learning new stuff

[@SchrodingersBox]

Glad you liked it!

[@CHIBA280CRV]

Another excellent lesson, I used your teaching on my vehicle and found the same problem.. Saved time and money by using your experience and knowledge on voltage drop..thanks again...

[@user-pe8lm2qk8u]

Hello! I am Korean. Your lectures are the best. Thank you.

[@SchrodingersBox]

Thank you! 😃

[@maxgamer1480]

I've been watching educational videos for a long time now and I have to say this is one of the best videos I've seen. A good explanation is always memorable. Thank you for making this excellent video.

[@jamm197511]

Hands down one of the best videos I've EVER seen on the subject. Ty very much. You have a gift sir

[@SchrodingersBox]

Too kind, thank you!!

[@marlinknable3543]

Thanks for a good video very well done! I'm a disabled mechanic and enjoy watching these videos to get my Automotive fix! This test reminds me when I was a young fellow before I was injured, my wife and I had a small boat, we had trouble starting it. But when I tested the starter on the bench it worked fine! So I stuck it back on the engine same problem slow crank like the timing was out! We had trouble starting the boat from the time we got it. In fact I got it for a reasonable price because of it. And I was okay with working on it. So after putting the starter back on I asked my sidekick number to Saint to turn the key and crank the engine to see if it would start! Of course it did not start. So out of the corner of my eye I saw something move. Living in South Florida at the time I thought maybe a mouse was in the boat. So we looked could not find anything and I had him turn the key a second time. When he did the positive cable laying on the floor of the boat flipped around like a snake. I said to him stop when he stopped the cable laid still. I said to him Kristen try to start the boat. Same thing happened repeatedly again and again. I lived a short distance from a Napa store that was still open I ran over bought cable by the foot and new ends stuck it on and the boat engine cracked like a new one!

[@modallas8034]

Geeez, all I wanted to know was VOLTAGE DROP. However; the lead up was so long that I almost left. I'm glad I waited because voltage drop turned out to be more involved than I thought. You can't test for voltage drop across an entire system like battery - solenoid- starter - ground, but It's actually battery - directing of flow - cable to solenoid - starter - cable to ground. Then, testing voltage drops across your own test cables. I guess testing that your test equipment is in good working order should be the first test. Great explanation! 👍👍👍

[@wcombs1983]

Great video - thank you for taking the time to explain this. I can’t imagine how many starters have been purchased because of misdiagnosis.

[@Rickengle300]

I have modeled my home technique almost completely from yours back from when you explained your fasttec method. Thanks for sharing your knowledge and experience!

[@SchrodingersBox]

It will serve you well!!! There really is no better method.

[@Rickengle300]

I used fasttec on a crank no start back when you released that video. Battery was good, starter relay was good, it’s been years and I don’t remember every detail but I remember being stumped, all of the likely things kept passing their tests.. I fought the temptation to change crankshaft/camshaft sensors, and tested them as you would have suggested.. saved me a hassle because they both worked. I believe I found that I was lacking signal voltage or something it’s been a long time.. I ended up needing a computer for that 99 dodge ram. 60 bucks spent and a working truck so I was proud. Occurred to me yesterday while watching this video and learning something new to me..that I never thanked you. A non annoying KZbinr who understands what advice he gives. One of the best of all time. I don’t fix cars for a living but I fix my own And I’m a millwright so I respect mechanical/technical solutions and processes Anyways much respect and thank you wise teacher.

[@SchrodingersBox]

Great call not to just replace the sensors. Pretty rare that a computer fails but I have 4 videos where FASTTEC indeed showed it to be the problem.

[@JimMacko8]

I remember finding your videos a few years back and not having the basics down enough to benifit. it's great to be back and learning soo much from this channel.

[@SchrodingersBox]

Yes it works exactly that way. Once you get the basics, review of the material makes it more valuable by far! Gotta stick with it- it almost never comes clearly the first time around.

[@Booki89]

Another fantastic and informative video mate, Thank you for taking the time to explain voltage drop and how to test for it. I wish I knew this information when I had a previous car of mine, it would have helped diagnose a electrical gremlin it had! Thanks again!

[@GrandFunalleyMedia]

This is helping me test a slow crank issue I have after moving battery to the trunk. I think a voltage drop test will prove I have insufficient grounding. Great explanation. Excellent instructional methods.

[@kevinlewis8642]

I thought I knew Voltage Drop... this was an awesome explanation. Made it extremely simple. I now know more than I did before I watched this.

[@treeguyable]

Good explanation. Trade school covered voltage drop, Marine corps motor t school stressed it a lot. In trade school, starter bench load test in the 70s, actually had us jam a broom handle/ scrap of wood, in the starter housing, against the gear, as a viable test. Did it a few weeks ago on my Perkins diesel starter.

[@marredandback]

Started watching this video some time ago but didn't get past the first 10 minutes, came across it again and I'm glad I stayed for the whole thing. You explained this very well and I'm probably going to watch it again. Thumbs up.

[@SchrodingersBox]

Good job- most of these videos take multiple viewings before it sinks in. The vast majority of people will never understand this stuff so congratulations on sticking with it and thanks for admitting it too!! Hopefully it inspires others to stick with it.

[@digemsmacks5690]

There you are.. used to watch frequently but somehow got away. Just stumbled on this and glad

[@Skinbob4life]

This 33 minute video are gonna help me for the rest of my life working on cars! Thanks

[@SchrodingersBox]

Glad to help!

[@ryanhodges7101]

Hey Matt, I found your channel about a month ago. I have learned a lot from your videos and I appreciate you taking the time to make them. I hope you are doing well and I am looking forward to your next upload.

[@wjackstl]

I am very thankful for finding your channel.....it's good to know I'm not the only person who will go the extra mile. thanks again for the voltage drop video, I learned a lot

[@hey_youtubeim_back2159]

In the dozen or so videos that I watched trying to learn why my dodge cummins is hard starting yours by far is the best video hands down. The ohms test and voltage drop example is gold information . Thanks again for the great video and very articulate explanation

[@SchrodingersBox]

Awesome. Hope you start it!

[@Stambo59]

Lol, I was screaming at you in my mind watching the start of this video. Lucky I watched to the end before commenting. Very good explanation of voltage drop. I know a few auto techs that still have a problem with this. Another handy tool when looking for voltage drop in high current circuits is a non contact IR thermometer.

[@jmyers224]

Hands down the best voltage drop video on the internet. I go back to this one time after time to refresh, 👍

[@SchrodingersBox]

Glad you enjoyed it!

[@kaiahearn3683]

Your videos are always extremely helpful and so well explained. I really appreciate what you do for us and how you teach people not to just change parts, but to actually test them first and understand the why. Thank you

[@SchrodingersBox]

I appreciate that! Thanks for watching.

[@rabbitweasel]

Love your explanation of the voltage drop. I now understand more than to do a test under load but now also why.

[@adriansaldana160]

Voltage drop testing was probably the only thing i had issues with. This was the best video ive seen so far. Cheers brother

[@Toast4Toasty]

I very much find this video helpful. I have been currently diagnosing a low power(rpm drops a little bit then rises up after an immediate hit on the gas pedal) car. I've pretty much been through almost everything(from all sensors, ecu, cat converter, ignition coil, fuel pumps, compression test and all that). Also I've even suspected a broken teeth of a bendix drive because sometimes the starter just slides but when I checked it everything's fine. Now, I've been researching about "voltage drops" and just came into your video and that explains all my observations that I have a bad wirings at least in the main positive line(it's reading 700mv at idle) and I am having a hot positive wire. I temporarily installed a jumper cable from the battery to the B+ of the alternator and it is now reading 100-200mv which is ok for now just for testing but I will fix all that and hopefully the low power issue is resolved. Thanks alot for your video...I love electronics since I was a kid and not an expert about it but your video gave me a clear vision on what to do next. Thank you once again.

[@coryjohnson3750]

A whole semester in electricity I couldn’t understand voltage drop. After 30 minutes of your video I now feel confident. Thank you!

[@SchrodingersBox]

Glad it helped!

[@subratabn]

Absolutely brilliant explanation of the entire concept of the voltage drop test.

[@franciskang2950]

Awesome explanation for voltage drop and clear practical verification for that. I appreciate your lecture!

[@waiting4aliens]

Damn, I have wasted so much money. This is one of the most educating videos I have seen. I didn't know, what I didn't know. Thank you.

[@mrghiax]

I love your starter motor circuit scenario, all too common costly mistake. It is surprising the amount of people that rely heavily on ohms testing only or worse still guessing the problem cause! Very easy to understand explanation of how voltage drop actually works. You certainly have a great talent for simplifying otherwise difficult to grasp components and situations Matt. This is one of my favourite videos on this channel.

[@SchrodingersBox]

+mrghiax Thanks man! This is one of my favorites too. It hopefully helps get the point across that the testing most people do on motor circuits is insufficient.

[@goldCrystalhaze]

I subscribed to your channel because in only a few minutes you proved to me that my basis in electricity is zero, yet my concerns for many years were to understand Maxwell's equations....

[@georgeheri895]

Great explanation, and example. Bad wiring has fooled many, and will continue to do so unless voltage drop method is employed. Thanks for the time and effort you put in to the demo.