Look at the small 4-pin connector on the side of the generator's case. If there is a single brown or red wire, (I can't remember), the voltage regulator gets its sensing voltage from the output wire. If there is a second wire in the plug, system voltage is sensed in the instrument cluster. This is done with digital dashes because the voltage there is more critical to prevent flickering brightness. There can be a different second wire, (white as I recall, but not certain), that is used for a tach signal for diesels.
Based on your previous knowledge, I would replace the generator, then, if the voltage comes back to normal, trot over to the dealer and stick their noses under the hood. Unlike the older generators from the 70s and early '80s, the voltage regulator is real hard to replace in the '87 and newer units, but it isn't impossible.
If you have a second wire in the plug, you might try disconnecting the plug, then run a wire from the battery positive through a small 12 volt light bulb to the generator terminal corresponding to the red or brown wire. You could also just remove the second wire from the plug if you can get it out without destroying it. It should regulate voltage internally this way. If the voltage comes down, look for a break in that second wire. I might be getting confused, because an open wire would be interpretted no differently as no wire at all. Perhaps low voltage, maybe due to a corroded connector pin, would make more sense.
I probably shouldn't be talking about that second wire since I don't know what goes on inside the voltage regulator's mind.
Tuesday, March 16th, 2010 AT 5:19 PM