I recently found a headlight switch with the fog light option at my local junkyard and I switched it in my truck from the oem one without the fog light option. My truck is a 2000 f150 single cab it has no wires behind the bumper but when I pull the new headlight switch out the indicator for the fog lights comes on. I cannot find a wiring schematic for the switch (or maybe I have over looked the one I need). I will add my own relays but I don't know which wire to hook to from the headlight switch to the relay. Any help would be greatly appreciated!

 

Well it's not as simple as your thinking.
In a stock system with Fog lamps, the Lamps are not allowed to light with high beams on. This has been a standard for many years to at least back in the 80s.
My advice is to get a copy of the Haynes repair manual #36059 and check out page 12-24.
There you will see how the Fogs are handled with a separate relay that only powers up through the main light switch and multifunction switch in low beam position.
There are color codes shown for wires and fuse values etc.
Basically you would come off the multifunction switch to a fuse, to a relay.
You will need to be sure a lead from the main light switch to the muti is in place as well.
the Fog lamp part of the switch is shown separately for convince where it's part of the main light switch you just obtained..
Otherwise do the old trick of separate switch and relay, independently.
Hope this helps. Good luck.

 

I don't know if this would work but I would just say screw the fog lamp deactivation feature and let it go all out. I accidentally back tracked a wire once and it ended up Turing on all 6 lamps like a freight train. I don't think it would kill the electrical just make sure everything that draws power is somehow hooked into a fuse.

If you pull the switch and the fog lamp indicator comes on you're in good shape to wire it up and don't need to do any work before the switch

 

Bluegrass, if I ran my own circuit as far as the relay and wiring for the lights and just tapped off the indicator light wire for the signal for the relay, would that be a possibility? I don't mind if it doesn't work with my high beams I just don't want to add another switch.

 

If you look at the circuit, that is what is done in the OEM circuit.
The switch operates a relay.
The relay is supplied power through a 15 amp fuse to the relay contacts that pass power to the light circuit.
.
If your switch lights it's lamp, apparently the 5 amp fuse feeding it is in place.
Come off that fused power to a relay for it's power, then from the relay back to the switch where it gets it's switched ground to operate, assuming that ground is present or placed.
The rest is just supplying a fused source to pass through to the Fog lamps.
That's all there is to the OEM circuit.
Now the multifunction switch will not allow lighting the Fogs in it's high beam position.
Always wire for safety, proper fusing and wire size.
.
A little extra; if separate yellow Fogs are desired, then change the output light circuit feed to go to a second relay.
In the dash fuse panel 'cover' install a flat rocker switch to be able to supply a transfer 'ground' only to the new relay to transfer power between the OEM lights and the other lights, at will.
It's would be right were you can 'feel' it and out of view for the most part.
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If installing separate lights, please take the time to aim for proper low overlap coverage so they don't blind oncoming traffic as these are only short distance fill in lighting for their intended application.
Good luck.