Does the black wire coming off of the alternator harness serve a purpose? If so, where does it go? Standard CS130.

Ken

 

Are you sure it's black and not just greasy? AFAIK, the alternator harness on my 91 system only has 2 wires.. the red one and the brown ignition power wire. My 87 harness has another one for the gauge, but it's still not black. Or are you talking about the one that goes into the junction block from the BAT terminal?

 

I too have the big red wire and brown wire as you do. I looked on the alternator harness and the letter "F" is assigned to that black wire. The GM manual says the black wire can be connected to battery voltage. I've ran without it connected for years and wondered if it makes a difference?

Ken

 

Is there any indication that the connector was replaced in the past with a generic one? That wire on the F terminal is SUPPOSED to be the brown wire.

There are 4 terminals in the voltage regulator... S for the voltage regulator's voltage sensing circuit, F for the field circuit, L for the warning light or gauge (our gauges get a signal from a different source so it's not used), and P, which, IIRC, is supposed to be for some sort of ECM or other computer control over the alternator. Either way, the diagram I have says that the F terminal is unused in the 91.

Someone correct me if I'm wrong... It's been five years since I attended a GM electrical class...