Voltage Drop Testing ~ The BEST Way To Test Wiring
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- เผยแพร่เมื่อ 6 ธ.ค. 2018
- Performing a voltage drop, or volt drop test is the best way to check wiring. If you are checking wiring for power, checking for ground, or an open, you can use volt drop testing. Volt drop testing is the best way to check a wire. Resistance testing of a wire does not properly test a wire
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True of False, Voltage Drop testing the best way to test a wire? ;) Links to everything we used today in the description.
Not to be one of those but you left the description from the last radiator video in this one🤭
Thank you! Freaking YT has been silly for me lately. LOL
Found faulty engine wiring harnesses via this method 👍🏼
It is neither better nor worse than a resistance check. Had you checked the resistance check of your upper wire and compared to your lower wire, you would have seen that 0.2 Ohms is a HUGE resistance for a wire of that gauge and short length. The resistance and the voltage drop are exactly equivalent as they are related by the linear Ohms law equation. There is no “static” vs “dynamic” issue here. The only way that makes a difference is if you are dramatically heating up some part of the circuit as resistance does vary with temperature in most materials, but generally the change is very small in copper wire.
the resistance of the top wire is also .2Ω. The issue is static or dynamic or loaded vs unloaded. testing the wiring loaded is the better way in most every situation. I am sure there is some where it's not, but overall this is the way that tells more of the story.
The way i learned it is a v4- reading.
V1: battery positive to battery negative
V2: positive side to negative side from component( lightbulb for example)
V3: negative side component to negative battery
V4: positive component to positive battery
V2 + v3 + v4 should be almost equal to v1 ( otherwise your reading is faulty)
V3 and v 4 should be as low as possible (0.5 volt drop is acceptable)
Example:
V1 is 12.6 volts
V2 is 10.4 volts
V3 is 2.2. Volts
V4 is 0.0. Volts
This means that there is a voltage drop in the negative side of the circuit
Its a very usefull method to find electrical problems.
Same, are you Dutch by any chance? :P
MrDanMan klopt! Echt een handige methode die v4 meting.
@@markalpha8005 Ja, het is zo makkelijk maar ik kan m nog steeds niet uit mijn hoofd 😂
Yes you get the same result using that method.
Why is this comment so underrated. Fucking thank you🙏🙏🙏🙏🙏
In 10 minutes of watching this video, I learned better about this topic (testing where the electical issue is) than I did in school with millions of words, minutes and explaining.
Real
I just graduated and I feel like I should know everything about automotive electrical but I don't.
@@robbiesharp311I just got done with a 2 week electrical course and I passed and have a little better understanding but it’s still difficult to put into practice but over time I’ll get better
Resistance tests (when performed with a typical multi-meter), are performed at very small currents. Thus wiring issues like the "two strand" demo aren't apparent. That "mini wire" is perfectly fine for delivering a few milliamps. But it is insufficient for delivering much higher currents, so this voltage drop test is definitely valuable!
Technically, it was only about .265 of a reading with the voltage drop test itself, and the Load Pro actually did drop about .2 of a volt so the Load Pro DID give you a very accurate reading. It's an incredible tool, and this even displays that it is capable of picking up even very small readings.
This is a really good tutorial. I've been watching different ones for a few days and this one is pretty explanatory in a timely fashion
Generally I'd love to see more of any electrical systems diagnostics related stuff. Alot of tech channels tend to neglect this part of diagnostics so It'll be awesome if your covered it.
Great job! I'm gonna share this everytime somebody wants to load the parts cannon!
It is important to *stress to very beginners that the reason DMM meter shows negative sign shows up when checking negative side voltage drop test. Otherwise, excellent video and I think I should watch one more time in a couple of days.
Oh man this brings me back to the RQC 2014 round 3. Great job on your breadboard man.
This is a great pictorial representation of how a circuit works - great job. One of the best explanations I've seen.
Great video man!! Some bad ground videos might be interesting also.
Thanks much for the explanation. 👍 in fact, I went out and purchased some of the items you listed just to create my own circuits from automotive schematics just to see how they are wired and to be able to create my own faults. I already have the load pro but this gives myself a great way of learning exactly what's going on. Great video and please keep them coming. I only watch certain guys and gals I know I can rely on and yourself Bogi, Paul D, Eric O, Keith D, and Ivan at PHD are the best. Thanks much ❤️️
Videos like these are my favorites.
Thanks for sharing the knowledge.
AWESOME!
This video was brilliant, very helpful and straightforward, all the others I watched they made it confusing but this makes it simple, thank you
Thanks for the video! I like the Load Pro myself.
Good video! You learn more clearly this way.
I’d like to see some videos on ground dropping I thought this video was excellent thank you very much I’m certain I will be using this information in one of my future videos and I will give you a shout out! ( not that you need it lol ) Love your stuff one of the very few people even watch on TH-cam
I passed 104 Electrical course! Not only did I pass, I also was a in the 100 club. Honestly your electrical videos helped me understand it a lot.
I got a %30 on my second quizz, and when I retook the quizz at the end of course when they allow one retake, I scored 80%.
In total 90% final quizz, 57 out of 60 on Lab final (forgot to convert to miniaps from minivoltage), and a 100% on my written final.
The instructor tells the students this course is the highest failure rate, and it really is, and is unnecessary stressful.
How was your lab end course like? Im currently on my 2nd week of elc course
there is an error when you measure the voltdrop it is 0.26 from memory but the video shows in big writing 2.6V. also when you talk about potential difference , you imply that there is a potential at each test lead, however i believe that the potential exists between test leads. Thanks a lot for the video, well explained :)
EXCELLENT!! Alot of this same info is in BMW's Standard Training manual for advanced vehicle diagnostics. Voltage drop tests are superior to ohms checks. The standard is 0.1 - 0.3 mV. Great Video!!
Thanks for making this video. I was struggling with the subject, but seeing it this way has helped me better understand it.
I would highly recommend grabbing your meter and trying it. Even just doing a cable to battery post test just to put the leads in the right spot
Very well put together! I'm surprised this doesn't have more views; it's very handy to know!
Thanks! Lot of people just have no idea this is a thing. Or is sounds scary LOL
I don't know if this is the same in each country but this is (a little bit) similair to the method we learn here.(the Netherlamds) V4 method. Wich is where you measure 4 things.
V1; the battery.
V2; the component.(in this case the H7 bulb)
V3; the positive cable
V4; the negative cable.
This way you always know where the problem is.
Btw love your vids Charles. I am working since the start of my career(age 19) at a VAG dealership(Seat&Skoda) and I can relate to a lot of stuff you are telling about in your videos.
Nice video! I can see you put a lot of hard work into this one.
Thanks my dude! This is one of those I wanted to be sure to get 100%.
@@HumbleMechanic I have 2006 ford super duty. Instrument cluster problem and windows radio problems sometimes work
Ok and sometimes not. What's is your recomend.to do
Very well explained, so I just subscribed to Ur video! Well done again!
I'm trying to self learn and advance from my current technical abilities. This demonstration has made it so much clearer and easier to understand.
Many many thanks! Great job!
Great video Charles.
Yeah i'd like to see more from the board, i'm quite keen on learning from you.
Load Pro is a great tool. Thank you for including it.
There seems to be some strong feelings about that tool. Lol. I knew I’d catch hell if I didn’t include it.
Very good content. I've been preaching voltage drop testing any time I'm dealing with issues in automotive electrical systems. My 2017 Fiesta ST that I bought earlier this year was a 1 owner car, me being the 2nd. Came out into my garage after driving the car and the driver side headlight was still on. Found a frayed wire in the harness (I'm assuming the previous owner ran a wire or something through the same grommet as the harness, because I found a slit in the grommet). Busted out the meter and found the offending circuit. You couldn't see the damage to the wire until the harness was twisted a certain way. Cut, solder, heat shrink and good as new. I'd rather just repair it myself than have to deal with dealership shenanigans and not being without my car for however long.
Long story, but anyway, proper diagnostic and testing procedures will prevent misdiagnosis. Makes me miss working on cars for a living, but I enjoy not starving to death! Keep up the good content, especially diagnostic info. Very useful!
Not starving to death? Is the pay or hours that bad?
@@starbai410 Pretty terrible considering the amount of training and experience you need. Mechanics on average earn less than the average wage. Yet it requires 3 years of training and then another 3 years experience to be ok at the job. Then its a pretty toxic environment with all the oils and fumes. That being said you can make a lot of money if you get good at the job. You could earn twice the average wage if you work hard and educate yourself.
Charles you do a truly wonderful of explaining concepts without being douchey about it what I don't understand is for top wire between the two exposed areas why the voltage isn't ~12 volts
Good example, thanks for the Vid.
I like how I went to 2 years of auto and diesel mechanic schooling took 3 electrical classes and didnt actually understand how to do a voltage drop test until I watched this 1 video wow thank you for the video I do actually understand a lot better how to do this test now
Outstanding video. Great info.
Impressive video, it's entertaining and easy to follow. In my opinion one of the best explanations on voltage drop i've seen.💪😊
Thank you so much
Yes it stimulate the mind in the right direction no complicated bullshit
going to be recertifying for ASE master in a few weeks. Thanks for the clear information
Good video!
Could be dangerous to those that do not understand modern electronics though however those folks will get them selves in trouble regardless if you made this video or not.
One of the scariest tools in a rookies hands these days is the Power probe.
I've earned bucket loads of money fixing vehicles after the owner or other mechanic fried modules probing wires......
As always, thanks for the great video!
Great Info Man! Thanks, My head lights swith is getting hot and I dont recall feeling it like that before. I wil use this to test the wires;;,💪👍
Great video mate! I would love to see more in this style from you :)
Thanks! These are fun videos. But like the current draw vid, a lot of people are stuck on old, outdated, or just any newer or different way to do things. LOL
@@HumbleMechanicGreat video. A nice follow up would be "what to do after a failed voltage drop test"
We had some odd ball electrical issues a few weeks ago. Did the voltage drop testing; that "failed". So we cleaned the battery terminals, battery cables, alternator connections, ground to engine, ground to frame. We also had battery & alternator checked at local parts shop. Car runs better and no electrical issues.
I appreciate these helpful videos. My weak point is definitely electrical, but I'm trying (:
Great video bud thanks man👍🏻
thanks for the video, i will use this to troubleshoot my voltage drop issue
Yet another well presented and informative video from The Humble Mechanic. Having an electronics background this is something I’m very familiar with, but I have to say you presented the test, and reasons for doing so in a way that the layman will understand. Top job Charles 👍🏻
Thank you so much
I'm in course 104 Electrical at UTI. I scored 100% on my first quizz, then a low score on my second quizz.
I'm not a good learner by reading. I'm a hand on or visual learner. I didn't have the opportunity to visually see or do a hands on for this second quizz.
This video helped me a lot to understand it better. I can check ohms like a pro. The rest was super confusing. But, this video's demo is great.
I'll let you know if I pass with a better score on my retake of the quizz. If I do, it's because this video.
Love the demo board!! Keep it!!
YES!!! I was thinking of looking at current draw on a regular bulb vs an LED bulb....
Great video. very well done!
Good video man! Nice to know I'm not the only one still sporting the 16 year old UTI meter!
This was awesome, thank you!
Great video!!!
Thank you SO much for this video! I have a mk2 Gti that is only reading 10.2v at the power lead for the lift pump/in tank pump, and I want t sure how I was going to determine where the issue was. I have a solid 12.5 at the fuel pumps relay, so I guess it’s time to start probing downstream of there until I find the issue...
I really appreciate the mansplaining, before this video i didn't know what Drop Testing was. Thanks! 👍
The Fluke 117 multimeter has that load probe built into the meter. It's a very handy function.
very relatable explanation 👍🏻
Great explanation
My favorite voltage drop video
Why did you equate .26v to 2.6 volt drop? Thanks! 4:37
I stopped the video at this time . Not serious.
I may be wrong but I think it was a typo the actual result was .26, which is how much voltage was used between the 2 testing points I believe anything pushing a bit over .200 volts is kind of bad
This would be a neat one to see in flir.
Thanks for your help
Love my LoadPro® I got a 48 volt capable set.
Thank you so much! Hoping I can use this to confirm if my passenger HID is flickering and failing to ignite due to voltage drop. Installing relays didn't make the difference I had hoped. Guessing it's an issue with the connector.
I LIKE THE CRIMPS ON THOSE CONNECTORS.
What do you call PRODIGY and INTELLECTUAL AND SUBSTANTIAL add one more KNOWLEDGEABLE the answer is HumbleMechanic
My teacher
Amazing thank you for sharing what you know with us. Thank you very much helpful video 👌 👍 please do part 2
Take care and have a great day
PRODIGY HumbleMechanic
From Nick Ayivor from London England UK 🇬🇧
I just want to let you know how awesome you are and that this video was awesome as well. Good day sir!
Thanks so much!
AWESOME videos' your methods are fantastic, much gratitude, please keep posting them, BLESS 😇👍
Thank you
@@HumbleMechanic will be watching everyone of your video's, be BLESSED, take care.🙂👍
Be interesting for you to do a vid on why bad grounds cause erratic symptoms...and why v drop doesn’t.
Oh we can make some bad grounds. LOL
HumbleMechanic
I had an old ford truck parked in the weeds for about 8 years, then give it to my oldest son.
The sheer number of bad grounds were too numerous to count... truly unbelievably high number.
Most concerning was the near under-dash fire, not to mention the innumerable system failures.
We simply regrounded everything from small to battery to chassis, to engine etc etc.
Lucky my son is an experienced HVAC tech with loooots of energy... I’d have simply junked it !
Was a great learning experience for me...never would have expected that many grounds would have been bad
I believe you can voltage drop ground cables as well.
Very interesting , Thanks , Could you do the same test and also measure the current draw difference between the 2 circuits?
I've been messing with electronics/electrical and using multimeters since I was a teenager, over 20 years, I even went to school for it, and I never knew you could get any kind of reading at all by putting both probes on the positive side of a circuit... Mind= Blown
One more tip: 0.75mm2 (18AWG) copper wire, 5m long (16.4ft) has a resistance of almost exactly 0.1 ohm. I don't know how thick the thinnest conductors, used in cars are, but probably more than that (0.75mm2 or 18AWG). So, if everything is good, you should get less than 0.1ohms on your multimeter, when measuring the resistance of even the thinnest wire @ 5m (16.4ft) long. And since most multimeters aren't accurate to more than 0.1ohms, if you get more than 0.0 or 0.1 ohms, you're not making a good connection with the test leads or there's probably something wrong with the wiring. Good video, btw! PS: thinner / longer wires have more resistance and thus more voltage drop, than thicker / shorter wires. And you get more voltage drop on wires with heavier loads (higher currents).
Thanks for the video Charles, always love your content. I'm just about to finish tech school myself and my electrical class wasn't very helpful.
Basic question: how does a 0.26xx reading on a DVOM translate into a 2.6 voltage drop?
nobody like s to admit mistakes, hence the no reply to your comment
Awesome 👌 video this is very detailed on voltage drop testing I use it in my automotive diagnostic I have a resistance on a brake light when the brake switch is depressed I changed out the brake switch with a new part and there is still resistance in that brake light the switch is not the problem should I do a voltage drop on each wire of the brake light wire?
Nice video! Electronic principles at their finest. Make sure you never test resistance over a live wire though. You'll make sparks.
ZAP! LOL
I USE THE LOAD PRO TOO GREAT TOOL.
Thanks that's amazing great experience videos channel I like it this post we love you too
I used to repair every gig I'd find in college,, instructors finally figured out it was me. ;)
Thanks!
SUBSTANTIAL HumbleMechanic
Amazing tutorial great video thank you HumbleMechanic
Please can you do Part 2 voltage drop testing 🙏 Thank you
From Nick Ayivor from London England UK 🇬🇧
Networking is the same... Signal degradation is experiences with voltage drop on the data lines that go over 300 meters.. Thus I use a fiber line. it can go for Miles because it uses Light instead of electricity. :)
Good explanation! I use voltage drop testing on almost a daily basis. Hell I just used it today on 3 different reefer units today to track down problems. One of the great parts about it is it can help you narrow down where the damaged wire is in the circuit moving from connector housing to connector housing. I have a load pro as well it is a handy tool but the only thing I don't care for is that it only draws about .24 amps. I would love to see a load pro that could do 5 amps or so for higher current circuits.
Load pro. I use that everyday working on liebherr's
I appreciate the work you put into this explanation, thank you.
Great video! How much of a load does the LoadPro apply to the circuit?
Good job! Stay humble
Great video, and very useful. Can you please make a video that explains your process for determining where to attach your leads within the circuit? If the frayed or pinched wire is somewhere inside eight feet of loom, what’s an efficient way to know where you have a good 12v or good ground source to locate the drop? Thanks.
for that situation going right to the component would be best. Look at how I had the load pro on the light bulb. OR really, anywhere you can get to wiring. LOL
Love your channel Charles! Question for everybody. I’m looking to get a beater vw, Audi, or BMW. I’m covered here with VW does anybody know a good channel for BMW?
Oh oh oh ok I have one for ya buddy! Yes! Voltage drop tests super effective! I've noticed you mentioned and also in my experience starting and charging systems do make for really easy guides on how it works and the basics. That will probably be the majority of time but! As a technician we know that these systems are also designed to use a certain voltage through a system. I.E. you dont really ever have just one headlight in alot of circuits So! With two headlight you would expect to see 6 volt loss across each one yes? Most modern circuits imo short of general starting and charging have more than one load designed in the circuit. Also! What if this a circuit that uses a 5v reference and common grounds for multiple sensors! This video needs another 12 and a half hour lecture to cover all the bases. I would love to see that video but in a collab with EngineeringExplained! Your both great guys and I love both of your channels but in a general shop environment I could see you guys butting heads quite often
Headlights are wired in series/ parallel, so if one blows the other stays on.. So when testing each headlight at connector you would see 12 volts.
Once upon a time I had a car. At night it was very noticeable that every light (Anything that was powered) would fluctuate in brightness in a consistent and constant manner. Motor ran good apart from the ticking noise. got rid of it as I needed a truck. Easy fix. :)
Hey boss.
Currently looking to buy a new labscope. My Snap on Vantage Pro took a shit after 13 years of good use. Although I'm really not wanting to drop the $$ for another Snap on product, they offered me a Vantage Elite brand new and updated for $1000.
Wanted to see what you prefer and would personally recommend
Shouldn’t resistance be measured with the wires disconnected. You are measuring if current can flow freely between the two points. The metallic connectors (seems like quick disconnect) can still effect the reading. I think if you would have disconnected the wire the reading oh ohms would be much higher
Great video! Any idea how you'd test the voltage drop along a wire connecting a DC-DC charger that is 7m away from the starter batter?!
i would love to let you use my fluke 87. ive found a ton of bad connections by checking resistance. maybe its more sensitive than the snappy idk. i also have to say i love my power probe but it seems to show extremely weak circuits as good and ground connections out of thin air lol
Would it ever be useful on testing signal wires? For example, I had a vehicle with a issue of randomly loosing power. 1 fault for Wastegate actuator posistion sensor - Low. Did resistance checks from turbo actuator to ECU, all OK. (I soon found out how useless resistance checks are) Eventually I found the 5v and Ground rubbed through in the loom which caused them to occasionally short causing a 'Low' signal, thus throwing a code. My question is, what would be the best way of diagnosing this if I hadn't found the chafed wires? As the ECU wiring is all enclosed when it's connected and running.
LoadPro It’s bloody good basically the way it works it applies 10 mA load for every volt up to 28.5 V
Good vidiyo
noted
great info. i was an ohms guy. im going to keep you around. lol
That method has its place. This is just another arrow in your quiver.. Well more like tool in the tool box. HAHAH
When I started out as an apprentice, all I learned was ohm and continuity. Took me several years to break that habit.
why was there voltage drop across the broken wire if it's not a load? Is it because there is less current flowing through that portion of the wire because it was only 2 strands?
I'm trying to learn how to check the circuitry of my son's 93 Honda. The battery drains overnight, but how?
The dummy battery light comes on, but turns off when the AC is turned on, so that's telling me that the problem lies in the AC. Is my way of thinking correct? That's all I'm really asking. . . . for now.
Thanx for the illustration of the broken yet still working wire. Very well done.
In order to fully understand this you need to understand the basic equation: Volatage=Amps x resistance (V= I x R). Voltage and resistance are indirectly proportional so when one goes up the other goes down and visa versa. So if resistance goes up (fault in circuit), voltage will go down; hence voltage drop
I think a scope and square wave stimulation is better than voltage drops for bus and signal wires. Much more sensitive. But for power and ground wires, voltage drop if more practical.