Volt regulator

Im having issues with low amps, amp light is on in the cab and guage is reading low. Alternator was rebuilt in the past couple months, took a volt meter to the alternator and batteries and both look good. Im turning to the volt regulator next. How do I test the regulator? And can it be done with the alternator still on the truck?

Thanks for any advice.

I looked for a message thread I read last year but could not find it. Here is a link for how to test. I gave up on the 1g alternator and did the 3g conversion. It has been working great. After going through multiple voltage regulators that came out of the box not working or would only last a couple weeks it was not worth the time and expense to keep messing with it. That is just my opinion.

Schnepel said:

I looked for a message thread I read last year but could not find it. Here is a link for how to test.

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I gave up on the 1g alternator and did the 3g conversion. It has been working great. After going through multiple voltage regulators that came out of the box not working or would only last a couple weeks it was not worth the time and expense to keep messing with it. That is just my opinion.

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I have a internal regulator built into the alternator.

I put my multimeter on positive battery terminal and grounded here as shown in picture and got 7.8 volts. Its low, anyone know if this shows my regulator is bad?

If the engine is running, I would say "yes". If it is not running, you have to replace the batteries.

DaveBen said:

If the engine is running, I would say "yes". If it is not running, you have to replace the batteries.

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Both my batteries read 12.5.

The engine was off when I checked the regulator.

I believe that ground text on that regulator connection is to show you what terminal to touch to ground with a test wire. This bypasses the regulator output, forcing the alternator to full output. It is used to verify if the alternator can provide power. If engine running, you should see a lot of current go to the battery, voltages increase, lights brighten, etc.

The other terminal should go to key-on power. Do not ground it, but you may verify with a voltmeter that you have battery power available there when you have key on.

The reason for key power is that with the engine off, the alternator can't generate any current with no mechanical shaft work to spin the armature. The voltage won't come up, the regulator will try to drive armature current to call for more output , which won't happen. No shaft work - no power out. So the regulator will continue to fruitlessly use battery current to power the armature until the battery dies.

It's a quick way to find out why no power. If shorting the indicated node to ground while the engine is running brings power full on, it's obvious the regulator is holding it back.

This is when clamp-on DC a meters ( optional ) come in handy for measuring the response, but for practical purposes just a quick touch is sufficient. Don't wire to ground as a "fix". A battery overcharge will be inevitable.