How To Easily Check Alternator Diodes

Watch at proclaimliberty2000 how an alternator with normal voltage output can drain the battery on your vehicle. This video will save you a lot of time, money and a big headache.

Disclaimer:
Under no circumstances will proclaimliberty2000 be responsible or liable in any way for any content, including but not limited to, any errors or omissions in the content, or for any loss or damage of any kind incurred as a result of any content communicated in this video, whether by proclaimliberty2000 or a third party. In no event shall proclaimliberty2000 be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits arising out of or in connection with the availability, use or performance of any information communicated in this video. Due to factors beyond the control of proclaimliberty2000, it cannot guarantee against improper use or unauthorized modifications of this information. Proclaimliberty2000 assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Use this information at your own risk. Proclaimliberty2000 recommends safe practices when performing any do it yourself repairs and or with tools seen or implied in this video. Due to factors beyond the control of proclaimliberty2000, no information contained in this video shall create any expressed 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 from the information contained in this video is the sole responsibility of the user and not proclaimliberty2000.

[mitchelllloyd]

Minor correction, the voltmeter, set in continuity setting, measures continuity in ohms resistance. A diode is a one way resistor to AC current. If you get the leads wrong as you pointed out, a diode has infinite resistance. In the correct orientation a diode will have something in the neighborhood of 450-500 ohms of resistance, a shorted diode will have very little resistance and an open diode will of course show very high resistance or infinite resistance. The important thing, and I thank you, is teaching me how to test my alternator easily. Good video, good instruction giving.

[markaltosmith]

Thank you very much for this. I have a parasitic drain after the car is switched off, which drains the battery in 15mins, the volts drop from 12.6 to 7 volts . Then I disconnect the negative terminal & the volts return to about 11.5. I will follow your instruction to test the diodes. Best tutorial ever, thank you again.

[pfoxhound]

Your videos are very informative and short. Only necessary stuff! 👍👍👍👍👍

[notlategame]

Just when I was gettin' used to Red on Red and Black on Black ! ;-)

[NextLevelAutoDiagnosticsLLC]

Did you even check where you plugged the leads into your multimeter?

[zio]

Great video, just what I was looking for...!✌

[RelaxingVibes]

Very informative video, thank you very much.

[chrisr.]

My 2001 Toyota camry is at 11 volts. I changed my alternator with a new alternator and it's still at 11 volts with a load? In this particular alternator the voltage regulator is included in the Alternator. Kinda frustrating I cant figure out what wrong with it. Battery is good. Just for some reason its at 11 volts with a load. Any ideas sir? God bless 🙌 and may the one and only lord bless you.

[eriksony]

Hi Paul, What car brand did you work with more? We want to send a good scan tool to you.

[bltoth]

Mr. Paul, can you show us how to identify and replace the bad diodes? We live in a throw away society and this could help. Thx

[chadmason]

First test does not isolate the alternator. A bad reading could be from anything in the car including the hood light being in the on position. Also this will not indicate an open diode only a shorted one. Shorted alternators are easily found with a standard amp draw test. Just disconnect the alternator and see if the draw goes away.

[lmo]

Well, now we know what a 'good' diode-pack reading looks like. But what does a 'bad' diode-pack reading look like?

[MrMac]

Its NOT the forward voltage you are looking for, its the reverse, which you should read zero. since there are
6 diodes in a alternator, you need higher voltage to test the back current. Also remember diodes react differently
at higher temperatures, when back current breaks down. Best way is a scope when running, under a load.

[rustycalvera]

ckecking my alternator with multimeter, ( negative probe on pos battery terminal, negative probe on alternator case) reads 440 millivolts. When the alternator/battery is checked at an auto parts place, their meter says charging at 14.4v but has a shorted diode. Is the miltimeter test limited as to what it can detect?

[likits]

Good afternoon my friend,
My battery is in the back of the car with the negative cable disconnected. When I touch the negative probe to the alternator positive cable and bolt and the red probe to the alternator casing, the multimeter stays at 1. When I reverse the polarity with the probes, the multimeter still stays at one. This whole test wile the plug and cable are still connected to the alternator. Thanks in advance!!

[adriancordeiro]

So I just did the first one to my 2001 Honda Accord and it read .316 so thats a bad one right ?

[kasujjajoeph]

Meter set ti continuity to test diodes for resistance but why are readings in mV pliz

[chriss]

Mine reads 998 so I guess it's bad and it ruined the battery also. 😡 These batteries are robbery now around $200.

[Tgilbert]

I can't get a consistent reading...One minute it says 400-600, sometimes it says negative 900 🤷‍♂️

[allywilkeforsenate]

Most people usually replace the alternator me cause azzhole manufacturers and alternator shops wont sell them too you.