misterious wires

[LCAM-01XA]

Actually, may I make a request? Those of y'all with trucks around made around 1990, can you please look under the dashboard and see if you have yellow wire coming off the BOO switch in addition to the two green ones, and if you do can you please try to trace it and tell me where it goes on your truck? Thanks!

 

[JPR]

This is how my controller is connected
from the firewall
- Blue - to the trailer brakes
- Red - 12+ power to the controller
- Red/Light Green - trailer brake lights
from the brake light switch
- connected to the green (not the green with stripe) for the electronic controllers (not currently use)

 

[LCAM-01XA]

Okay, so the yellow wire is the trigger! Thanks man, it all makes sense now - guess they did want to overload the truck's own brake light circuit, so Ford made the trailer brakes draw through the controller, and since an aftermarket controllers don't have that feature my truck's previous owner splices the trailer brakes straight to the BOO switch. Good, I can sleep better now, lol Thanks man!

 

[MF2003]

he red/green may be to power the brake lights when the trailer brakes are applied using the controller.

 

[LCAM-01XA]

yeps, that's what I figured - Ford used a separate circuit so to not overload the truck's own brakelight circuit. Guess the previous owners didn't have teh controller so they spliced the controller trigger wire to the trailer brake lights cause else the brake lights wouldn't work without that. When I get around to installing an aftermarket controller I'm gonna use the trigger wire to trigger both the controller, and a relay for the trailer brake lights, the relay will take its power off the same wire the controller does - basically it will duplicate the brake-light circuit in the factory brake controller.