Hi,
Just bought a 2005 STX with the towing package on it. I cannot find the "extra" wire in the bumper wiring harness to hook up my cap brake light. Anyone have any idea where to look? I don't want to rip all the wires open back there if I don't have to...

Thanks!
Tom

 

When I put my cap on, they put a wire tap onto the stop lamp wire to the stop lamp bulb on the left side lamp.

 

you will find eveything you need in this post (take a look at post#7)
https://www.f150online.com/forums/el...rake-wire.html

the rear brake/turn bulbs on these truck do not distinguish between brake and turn signal, so if you have your turn signal flashing then your 3rd brake light flashes too?

 

Post #9 got it right. Small light green wire on harness, under black plastic cover outside of frame. Under driver's left knee.