Alternator help please

[khamilton]

I have a non modified 24v cucv. Both stock alternators have been rebuilt by an Alternator shop a few months ago. Now they are not charging. Drivers side voltage at red cable 12.7v key off, 12.5v small red cable key off, 0v at Brown exciter cable key on. Pass side 25v large red cable, 12.5v small red cable key off, 12.5v at Brown exiter cable key on. All fuses are good in the fuse box, neither Gen light comes on when I turn the key on and both Gen bulbs are good and not burned out. I even replaced both Gen relays thinking they might be bad, but that didn't work either. Any help would be greatly appreciated.

 

[CUCVLOVER]

Are the plugs that go in the top of each gen ok?
I was having the light flickers on mine once and the plug was loose.

 

[khamilton]

Yeah, both plugs are good...driving me crazy lol

 

[cucvrus]

Check ALL the fuses. And check the connections at the back of the instrument cluster. Just because the bulbs are good does not mean they will light. You probably have a minor issue that will drive you crazy. I just had a plow truck with the Gen 2 light out. It was fuse. I did not replace it I had another guy do it but I think it may have been a 25 amp fuse for the wipers or something weird. I did not do it but he said it was a 25 amp fuse. Check it out real close. I am going to bet on the circuit board or a fuse. Good Luck.

 

[Tow4]

With the engine running install a jumper from the battery terminal on the back of the alternator to the #! regulator terminal (one on the left looking at the alternator from the rear). This will turn on the regulator and start the alternator charging if it is working. Do this for each alternator to check them. If they both work, you know the problem is somewhere else.

Here is a Delco alternator service bulletin that covers basic hookup and testing.

View attachment Delco_Alternator.pdf