Voltage Drop Testing the Charging System

See a quick, easy demonstration of how to perform a voltage drop test on the charging system of any car. This test will tell you if all of your wiring and connections to and from the alternator are good.

[wbudd]

Your clear description of what was being accomplished at each step made it easy to grasp the concepts. Well done and thanks!

[MartinX]

My books explain it in such a over complicated nonsensical way, this makes sense. Was completely confused. Thanks for the video

[seand]

I've watched over 20 videos on testing the charging system and yours is the best and most detailed. very well explained. Thank you sir.

[rubiconklbrutorowman]

Well done 2 showing us very clear n SIMPLE manner n ths again indeed!

[stevensapyak]

1.5.14. Great expose on voltage drop in a circuit. I was out in Wyoming July 2013. Such a beautiful ride thru the Big Horn Mountains! Not to forget the Beartooth Highway!!! I will be back.

[potgieter]

Thanks for the advice, i found an volt drop in my live side and fitted an new cable that fixed my problem, great video thanks

[automaster]

I would recommend 0.2 volt on each side of the circuit or no more than 0.5 volts for both sides. Also when doing this test you want to load the system either with a carbon pile load tester or truck all accessories on while the engines running.

[electronmarkboggess]

I like to turn every thing on to really stress the circuit..Seen a Vd of 3mV with no load other then what ever was consuming power to keep the car running.. Turned on the heater, defrosters, Head lights, hazzards, and wipers. Vd was then at 3.5ish Volts...removed cable and found a spot where someone cut a piece of insulation away to splice in a smaller wire to power a relay for LED light bar(why there who knows owner said he bought car like that).. Needless to say the cable within a few inches of that open was corroded with green oxidation through most of the strands...Nasty stuff!!! great video just thought I would mention that

[vintagefun]

Thanks for the video well explained. I did an alternator test on my 12 Acura TL and am getting 14.17v at idle and under load. I couldn't rev the motor as my wife is sick so didn't have a helper to add rpm but suspect it is working well. Will try the voltage drop test when I have more daylight. I did try the negative leak test and it was showing 0v and I did it just like you explained. Could not figure out which was the + coming off alternator. I just think that my 5 year old autozone gold battery is near the end of life!

[billlincoln]

Fantastic video. Very educational. Simple and effective.

[zhivago]

Excellent demonstration, i will try it on daughters car. She had a new alternator and battery installed but it was not charging. I had wondered if it was a wiring issue...

[nickayivor]

Very KNOWLEDGEABLE
The Auto Rules
Thanks 👍
From Nick Ayivor from London England UK 🇬🇧

[bandit]

...outstanding!...very well explained!

[Candoit]

Thank you Sir! Now I know how to do the test!

[CHIBACRV]

Very informative, can you make a video on showing the difference between the amperage being used by the vehicle system and what is leftover to maintain the battery charged. A how to test for that..thanks

[alanfarias]

Great video none of that “um ahh, um um umm ahh ahhhh ummm um ummmm ahh ah ah like like like umm, you get my drift. Thanks again great video

[kalvink]

Excellent and informative, cheers. George C.

[cavalierabouhamma]

Welldone, thanks so mich it is usefull and clear to me. God bless you

[pigeonsilsx]

i have a question.does the voltage drop readings increase as amperage increases?i seen a car that had a 2v drop on power side of fuel pump, the spec fuel pressure was 45psi but the pump was putting out a massive 90psi.would this cause a rise in amperage that would create a 2v drop?

[djpitr]

Good video, o got truck and I just changed alternator and now it’s having trouble charging, I have 1.2v drop on negative side, and way I could run extra wire from alternator case to negative post on battery? Would that help ?