If I'm not mistaken, the portion of the harness for those items is shared. I agree it could be a wire, but most likely it's a ground like Slick said.
Portions of the harnesses in these cars are routed horribly and subject to burns, rubbing and inadvertant abuse when servicing the car. Sometimes, the harness connector mounts break and cause strain on the harness wires and connectors. Add all the issues with valve covers leaking oil all over the place, all of the connectors may be in need of a good cleaning. You can get a decent contact cleaner almost everywhere.
I don't have anything that tells which part of the harness to focus on, but I'm sure someone else may have it.
