Does anyone have experience mucking with the factory fog light setting on the headlight switch ? I was testing to find the pin on the switch that controls the fog lights, and found no set of terminals that changed with the fog lt. on/off. The truck didn't come with fog lights, but I was hoping to use that portion of the switch for another purpose (aux. backup lts). The wiring diagram doesn't distinguish which terminal on the switch is used for fog lights, but it does show a wire leading to the multi-switch (logical, since fog lights only work on low beam). Also, the headlight switch troubleshooting chart in my manual doesn't refer to the fog lights either.

So, the million dollar question is : How does the truck know to turn fog lights on when you pull on the headlight switch with the lights on ?

 

The '97 to '9 MY trucks are a bit different in how the pull on the main headlamp switch to get the fog lamp relay coil to pull in the contacts.

Your MY truck is actually switching ground to the coil in the fog lamp relay, vs the newer MY trucks, and the "normal" method of switch power to the coil.

Pins #1 & #2 on the main headlamp switch are what are close together to make this work.

Pin #1 Black wire
Pin #2 violet wire

In your case to use it for something else, you are going to need to do the same thing, ground the coil on the relay via the switch, and have power constant to one side of the relay.

Functionally speaking, this is correct to do, just not "normal" int eh US to do, as it is not a Lucas Ignition System or BSA motorcycle ( BTW BSA = Bastard Stopped Again )

Here is the diagram, file save as and print it out.



Good luck.

 

Sscully, you're right, it is wired in an unconventional manner, someone at Ford has been taking lessons from Volvo or Bombardier, or some other dufus. Thank you for the info and diagram, I would have eventually realized that the only pin in the headlight wiring NOT being used would have to be for the fog lights, and since it's not a 12v switch, it would naturally have to be ground switched.

Thanks again, that's EXACTLY the type of answer I was looking for !!!