I have a 99 xlt 2wd, which did not come with fogs. I found a valence and fogs to put on. My question is I have the wiring at the bumper, but where is the wiring for the fogs inside the truck? If I replace my headlight switch with one for fogs do I also need to get a harness to plug into the new headlamp switch that goes to the fog relays??? Please help. I know how to wire them other ways, but would like to keep all this looking and working like factory.

 

I am half way through the same mod and found that all the wiring and relays were already in my truck (an XL) except the wire from the switch to the relay. I posted a question on this but did not get any answers. https://www.f150online.com/forums/sh...threadid=96734

Under the hood there is a wire from the relay box to the firewall but I could not find it on the inside of the firewall. I guess I'll be running a wire to the relay because it really does look like the under-dash harness has no provision for this. Seems odd to me, considering that Ford included all the other wiring and relays. Perhaps the body harness is common for all models but the dash harness varies from model-to-model. I would like to find a neat way to plug into the switch though.

Your XLT may have the underdash wiring - post and let us know how it turns out.

..............Scott

 

Read this:
https://www.f150online.com/forums/sh...threadid=96040

You should be able to use the existing wiring with a new headlight switch. Scott D's is the 1st one I've heard of that didn't work.

Scott,
Does the large connector that plugs into the back of the switch have 9 wires coming into it? If the wire comes out of the relay, then I doubt it just disappears into the firewall. There is a harness connector between the fuse/relay box and the firewall. The yellow wire goes through this, and there are actually 2 yellow wires that go through the harness so make sure you follow the right one. That's the only connection between the relay and the headlight switch according to the diagram. I guess it's possible that the wrong color wire was used, or no wire at all.

 

Thanks for the post Sven. That is the wire I was searching for. I lifted the relay box just to be sure it was going from the relay into the firewall.

I do not recall now how many wires were in the plug, but I did find the correct foglight connector on the switch (with ohm meter) and there was no corresponding connector on the plug.

I'll check the number of wires on my switch plug and try once more to find the yellow wire.

...............................Scott

 

Thanks for the replies, I ordered my new switch today, guess we will see what happens tomorrow, I will let you know.

 

Got the new headlight switch in and plugged up, low and behold we have fogs!!

Scott, it appears to me that the small gray plug that goes into the back of the headlight switch with I think 4 small wires is the set that controlls the fogs, that new switch I got has a pin inside where that plug goes and my original switch had no terminal there, eventhough the plug was pushed into there.