Posted here because car is 88 Iroc TPI. This car was damaged on the R Front at battery, and both fan relays were damaged or had cut wires. Problem is an extra all black wire no tracer color coming from a wire loom behind air conditioning pump heading towards the battery area and no wire to match. All other wires were in looms and easy to match. This car was cobbled by previous owner or friends. My assumption is that this is a ground wire, but would prefer some one to verify.

 

If you could take a picture and post it, identification would be a lot easier.

 

If it's a black wire going to near the relays and behind the ac compressor, it probably goes to the temp switch in the passenger side head, and controls the relay for the secondary fan. Is it a skinny wire, like about 14 gauge? It will look like an open with an Ohm meter with the engine cool, and will be a short with the meter with it hot. You can get a cheap Ohm meter from Walmart for $7 if you don't have one. Anyhow, that's my bet. (I just traced out a mystery black wire last week after doing my TPI swap, and guess what. )