Voltage Drop Testing the Charging System
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- เผยแพร่เมื่อ 3 ม.ค. 2014
- 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.
My books explain it in such a over complicated nonsensical way, this makes sense. Was completely confused. Thanks for the video
Your clear description of what was being accomplished at each step made it easy to grasp the concepts. Well done and thanks!
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.
Well done 2 showing us very clear n SIMPLE manner n ths again indeed!
This video was electrifying
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
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.
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.
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
.350 mV still isn’t a bad circuit.
Fantastic video. Very educational. Simple and effective.
Best demo yet 👍
Thank you Sir! Now I know how to do the test!
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!
Excellent video. Thank you
Thanks great video!
very good explanation thanks
Welldone, thanks so mich it is usefull and clear to me. God bless you
Thank you, this was helpful
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...
zhivago1955
What was the issue? I have a friends ford acting like your description
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
Very KNOWLEDGEABLE
The Auto Rules
Thanks 👍
From Nick Ayivor from London England UK 🇬🇧
excellent video's thanks ,,
...outstanding!...very well explained!
Excellent tutorial, thank you....
this video is exactly what I needed do you have more videos for chevy malibu. I have a 05 Malibu maxx and my charging system just went to shit without warning
good video amigo
Hmmmm.... you really need to have good current flow in the circuit under test to get meaningful voltage drop readings. To do so, with the engine running energize everything convenient in the vehicle; lights on high beam, HVAC blower on high, A/C on, rear window heat on etc. Note that there are numerous other voltage drop scenarios , and they should also be preformed with the circuit in question carrying it's maximum amperage.
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
Well explained
Excellent and informative, cheers. George C.
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?
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 ?
What is the formula of voltage drop in DC copper wire?
I have a 2006 Honda odyssey on the negative side it shows 0.2 volts as soon as I disconnect the negative side the millimeter shows it’s 11.6 but when i use a jumper cable it shows the alternator charges 14.5.
Nice!
wondering what kind of juice did you get from the ac generator? was it orange juice maybe! lol . Great video!
This has helped thank you!
i realize I am quite randomly asking but do anyone know a good place to stream new tv shows online?
@Jefferson Sean I would suggest flixzone. You can find it on google =)
@Dillon Emery yup, been watching on flixzone for months myself :D
@Dillon Emery Thanks, I signed up and it seems to work =) I appreciate it!
@Jefferson Sean no problem xD
My mother in law gave my son her old 1988 Mercury Grand Marquis that had been setting for some time and the amp light on the dash has been on every since he got it. We had the alternator replaced because it was bad believing that would make the amp light go out and no such luck. Then we replaced the external voltage regulator and put on a new battery ground cable and that was no help either. Also before that we replaced the battery. Could a bad body ground be what is keeping that dash amp light on? I’m going to do the voltage drop test on it tomorrow.
+busman54 yes I would think so or there is a short to ground in the light itself
Hey I test mine diode it’s reading 716? Is that good or bad?
So if theres voltage drop on the positive side, then check all the connections on that circuit?
Only if the voltage drop exceeds one half a volt, or .500v on any circuit.
what setting does the meter need to be on.
Brian Kelley 20 Dc volt
Thanks...
When you say “alternator output” are you talking about the B+ terminal or the D+ terminal? My voltage measurement between the battery positive terminal and the B+ terminal on the alternator is 0.00 VDC. Is that good?
He said anything below .5 volts on the Positive side is in spec. He said any Voltage below .2 on the negative side is in spec.
So If the voltage is > = .5v (on the +(ve) side of the alternator circuit) means that the alternator must be replaced, and if the voltage is > = .2v (on the -(ve) side of the alternator circuit) means that your connections are faulty? Great video, thank you.
Not necessarily. Eric from South Main Auto has a video with excessive resistance, high voltage reading on the positive side of the circuit. Bad connection from alternator B+ stud to the output cable. Bad design melted out over time and created resistance. He still had to replace the alternator because the bad connection design cause the alternator and output stud to fuse so he had to break the alternator off of it's mount. Find the part of the video where he removes the alternator th-cam.com/video/fYjuP8FBUu8/w-d-xo.html
Voltage drop wouldnt be the alternators fault but if its leaking ac voltage in it is
Chrisfix says to rev the car to 1500 rpms when doing this test . Is that necessary?
Yes. Alternators put out fewer amps when at idle, and rated amps at 1500 RPM or above. The voltage drop will be greater with a greater number of amps flowing through the wire. That high current situation is what you want to test.
Ty
Couldn’t you go to other connections on each side of circuit to narrow down the exact area of voltage drop?
If there is a problem yes. No need to test in many places if the whole negative side is within spec.
Yes that is how you find the problem
What holes do the leads get plugged into? Brand new multimeter user here
Com for neg. Black and v/ma for red lead
This is really late lol but the black is always going to be in the COM but the red is connected depending on what you are going to test. On the far right you use it for voltage, ohms and some other thing that I forgot and the left is for amperage
How about the voltage regulator, could it be a problem as well.
Voltage regulators when they go bad can drain the power from a battery when the engine is turned off.
Can you demonstrate how to full field an alternator?
Do you mean you want to activate the field output circuit? If that's what you mean, you apply 12v to the field terminal.
rusco321 I’d be careful doing that you can mess up the pcm
So what's a bad number reading on positive, negative?
anything higher than .3 00
I been breaking my head.alternator good
I still don't really understand how the volt meter gives a voltage reading when the leads are both on one side of the circuit?
That means there is a voltage drop across the two terminals possibly due to to resistance across the connection...
In theory it should be Zero volts. Resistance causes a difference in potential.
Most of the time your are going to find the ignition switch is intermediate. Check the starter switch first.
I connect it to positive lead But multimeter says 0 reading? What’s that mean?
Were these readings measured during a load or was there no load on the circuit?
Not much of a load
very good, but too long
great tutorial but is mising the voltmeter setup, not everybody know how to use it
What's the deal man, not teaching anymore??
Nice fluke
Your incorrect and mis-use of words and terms really causes alot of confusion.
Your video is almost 10 mins long. You video is absolutely filled with so much useless information. It should have been less than 2 mins max. Do we really need all that extra talking you throw in., think about it. It just waists people time.
I am trying to lose weight now that you mention it.
Dont listen to him your video one of the best and clearest