Help with fog light wiring

[StevenJ]

I have just mounted a Buckstop bumper and am mounting fog lights into the holes in the bumper. I want to use the factory fog light wiring to trip my relay for the lights. The factory fog wiring has a red and a blue wire. The red tests hot at all times even with the key off and the lights off. The blue does not get hot even with the switch on. Any ideas on how to use the factory wiring to trip the lights? I would like to avoid having to mount another switch. The lights are 55 watts each. I think the factory's were 35 watts. I don't want to overload the small factory wiring.

 

[Thomas]

Your OEM fogs use switched ground. The blue should connect to ground through the headlight switch when the fog position is selected on the headlight switch and you don't have the high beams on.



You need to hook the one factory wire to one side of the trigger coil of the relay and the other factory wire to the other side of the trigger coil of the relay. The relay should now open and close as the fog light switch is turned on and off.



I'll leave the high current part of the circuit to you since you only asked 'how to use the factory wiring to trip the lights'.



Post any more questions.



Have fun!

 

[StevenJ]

Just to be sure, I would take the red to the switch in on the relay and the blue to the relay ground?



Thanks for the help.

 

[Thomas]

Those numbers on relays and sockets are universal (by Bosch decree... ) terminal designators. You should find:



86 — the relay switching (control or 'trigger') circuit input.



85 — the relay switching (control or 'trigger') circuit output.



30 — the power circuit input.



87 — the power circuit output.



Hook the existing red wire to terminal #86.

Hook the existing blue wire to terminal #85.



Terminals 30 & 87 are the 'switch' in the circuit that contains the filaments of your new foglights.