So I've got this annoying charging system problem...
The volt guage reads half way between 8 and 13 volts. It jumps around apparently for no reason independant of engine rpm. I can set the cruise at 75mph and it'll go up and down, but it never varies by more than about 4 volts in either direction.

The alternator is new, the battery is new, all the grounds and power wires have been cleaned and had star washers installed both inside and under the hood.

I checked the voltage with my dvm and it seems to be charging fine with it connected, but after using the dvm the volt guage in the dash hangs closer to 13 volts.

I read up in the 87 electrical supplement and other GM reference manuals and it says the CS alt requires a light or resistor in the guage cluster to excite the regulator. I don't see a volt light anywhere in the dash. Is there a resistor in the volt guage?

 

Well here's what I have figured out... The alt charges fine if the L terminal is energized at startup. The wire from the L terminal goes into the wiring harness and runs straight to the guage cluster, pin 14 on the cluster harness. Now here's where it gets interesting... pin 14 doesn't line up with any of the printed circuits on the guage cluster.

So, as best as I can tell, the car should have an alternator that doesn't require the L wire to be energized, and currently the car has the wrong alt. From what I can tell I need to either add an idiot light between pin 14 and 12V switched, or I can replace the alt with a correct alt.

Anyone want to tell me if I'm right or wrong in my findings?

 

The best I can see is only on the vinF motors, the alt. had a 10ohm resistance wire (brn/whti) in the factory harness comming off the ignition switch and is paralled with the voltmeter wiring.
Try PM'ing Danno too.. he seems to know alts. like that back of his hand.