Voltage regulator question


New member
Conroe, TX
I've searched for hours and haven't found the info I'm looking for. The alternator on the passenger side doesn't seem to be putting out. It's sits right at 12.0v at idle and drops to 11.6v with the LED lights on. Truck has been starting slow also, which I associate with the low battery.

Checking from the isolated ground to the exciter it reads 12.0v on the red wire and 9.0v on the brown wire. I cleaned all the terminals and also cleaned the plug at the firewall.

Im thinking its a regulator issue, but need info on the regulator. Where is it located and what should the exciter voltage be?

Thanks for any help!


Well-known member
Portsmouth, NH
If it is putting out that voltage even after revving the engine, I think you due for a rebuild. I would recommend a good quality kit and do both Gens just to make sure the other one doesn't go south a week later.

snowtrac nome

Well-known member
western alaska
the regulator is internal the one wire should be 12 volts that is your exiter wire the other wire goes to your idiot light in the dash the large terminal should also read battery voltage with the engine off. The regulator and diode trio is an easy replacement. I have had several of those alternators fail and usually it is the windings not the solid state parts. the one difference between the commercial large frame Delcotron alternator and the military model is the military alternator's case is isolated and the ground is another wire on the back. other wise it is a large version of a delco alternator found on a 73 to 80 something gm product.
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