Well on my 91 RS, the factory harness has the pigtail for the switch and relay. So I figure the wiring from the relay must end somewhere for use on fog lamps; however, I can not find where the wires end in the engine bay. Does anyone know where to find the end?

 

Where does the fog lamp wiring split from the rest of the harness on factory fog light equipped cars?

 

On my car (87 gta) they are with the side marker lights. They are only hot when headlights and dash switch are on.

 

I have a 92 and I added the fog lights also. Bought the relay and the switch. In my little bit of knowledge it appears that the wiring is there inside the cabin. The fog light wiring for our models went through the C100 large harness on the drivers firewall. If it didn't come with foglights it will be difficult to add the wires to this connector. It's full of sealant so I gave up on adding wires here. I bought the brackets and wiring off an iroc and it had a grommet that went through the firewall. That is what I will be wiring into my relay and switch.

 

Well, I almost have it all in place. I found the factory pigtail for the fog light relay and the pigtail for the switch. I ran the power wire for the fog lights though the engine bay and to the relay. All I have left is to splice the power wire from the relay (which would have ended at c100) and connect to my new line. The only thing I need to check is that the relay ground will still work or if it dies off at c100 as well.

Edit:
Since the ground goes to the head light dimmer switch, I would guess no additional wiring is necessary.

 

You can add wires to the C100 fairly easily. That sealant is a real pain in the butt, but PB blaster desolves it (not like sugar in water, but it will clean up any mess). To add wires to the C100-
Engine side - use similar connectors from donor car, cut wire leaving 6 inches after C100 connector. Use needle nose pliers and pull until it comes out. It will come out. In the new connector, spray some PB blaster in the hole you plan to put it in, use a screw driver to poke a hole through. Feed the wire through this hole (backwards) until you can grab it. Then pull until the new pin clicks in. Splice the wire to whatever you need and viola. I had to rewire the wiper system using this method. 4 wires and it works perfectly, so it's not hard. The pin will sometimes stick up higher than the rest (slightly higher is okay for now). When you screw the connector back on, it will push it back into the block.

 

Which color wire from the relay do I need to attach my fog light power wire to?

 

Based on this wiring diagram it looks like the power to the fog lights comes directly from the switch. For some reason, I thought the power would come to the switch then to the relay then to the lights.

 

After reading the diagram, I think I can switch the yellow and light green wires entering the relay pigtail. Then, I would route the light green wire to the fog lights. Doing this should also allow fog lights on with high beams.

 

Fog lights on with high beams isn't legal. Most vehicle codes state that only 2 sets of bright lights may be used at a time (i.e. low beam - high beam, low beam - fog lights), that's why factory fog lights are normally disabled when the high beams are turned on.

This also applies to two headlight systems like the Firebirds have.

 

I realize that fog lights with high beams in illegal, but it seems that people go after that modification. I made a mistake with the wiring, but it is pretty simple. I should have switched the yellow wire to the brown and then attach the brown wire to the hot for the fog lights. This was done after switching two slots on the switch and changing one to a 12v hot.