For the last few days an electrical gremlin has popped in and out. I did have a headlight ground short that was found and fixed a few days before this happening

73 914 2.0. The generator-alternator light came on and the tach dropped about 1000 RPM (still work but reading low) and the turn signals will make the tach jump with the turn signal. When running the alternator is putting out 13.95 V and with the motor off the battery tested 12.6 V. Alternator belt is just right. Fuses ok. Checking grounds. Could this be coil related problem or ???

(from face book)
U could have a bad diode in alt causing the alternator trouble light to be on and still charge and other dash lights to fluctuate bright and dim. Test using a volt meter on AC to see if the alternator is putting out AC current showing a diode bad. I would also recheck all ground connections.

So me, Putting the voltmeter on the battery with the motor running it’s showing 30 V AC which could indicate a what? If the alternator is kicking out AC do you think that’s probably the culprit?

This is a 90amp rebuilt that Clay put on for me about 5 years ago. Other tests I can do? And any recommendation for a starter/generator rebuild shop in the Fort Worth area? Thanks All.

If it has a blown diode, you will see AC voltage on the battery terminals, and the generator light will be on.

The diode plate can be salvaged from another alternator to keep the 90a one working.

If you need an alternator for it, I have a few spares.

Clay

Thanks Clay. Check and check. Ac at the battery

I have one alternator but don’t know its condition. Is there a way to test the diode’s on that alternator with an ordinary meter ?

If you have AC at the battery, you have a bad diode. If you want to come over, I will give you an old alternator. You can disassemble it and take out the diode plate, and swap it into your high amp alternator.

We leave for Okteenerfest tomorrow morning, so it will have to be today, or a week from now.

Clay

Next Week is ok. Enjoy Teenerfest! and Thanks.