I finally found a set of fog lights for a 91-92 car at a junkyard, everything was there so I got it, switch panel, lights, etc. Anyway, after searching through some threads on here, I learned that the plug on the interior does indeed exist for the switch. Opened the switch panel on my Formula up when I got home, yup, plug was tucked away and covered with dried up tape from 1992, cool!
My question is, what should I go back and pull off the donor car? The entire wiring harness? I take it I need a relay of some sort, though I have no idea where it's mounted, and from what I've read here, it seems that the underhood portion of wiring doesn't exist. At what point/location do I have to go back and either start hacking or splicing? Does the wiring go to the fuse box at least? I want it to appear as stock as possible.
I thought it was interesting that when I hooked up the new foglight switch, power was already available for the backlighting- it lit up when I turned on the parking lights!

 

There is a separate fog lights fuse (which in your car will currently be blank) which will supply power to the purple wire on the switch connector that you already installed.


There is a relay, but I don't know where it's located. My guess would be underhood. If your car was pre-wired for the relay, the wire colors on the connector will be light blue, yellow, light green and brown if you can find that one.

 

Even if you don't find the pre-wired relay plug, that's the easiest part of the whole deal to get wired up. The switch and the fog light mounts are the critical items.

 

I did find a single, unused, red wire with some type of plastic connector on it, driver's side, near firewall. Is this the one that goes to the relay?

 

Not likely, a relay connector will have 4 wires.

 

Is this the fog light relay? This is on the driver's side firewall, behind it are two other relays. It has the four wires like you said...odd looking relay though.

 

No, that's the ESC module.
IIRC the fog light relay is under the dash above your right knee.
The red wire on the firewall is coming out of the fuel pump relay and you can hook it to 12volts to test the fuel pump.