Extra Green Wire on Factory Brake Controller Harness on a 1994 Ford F-150

Question:

Hello, on my wiring harness for a 1994 F150 the plug looks like the one on your adaptor and is color coded the same except I have an extra green wire on the truck side. Is this correct or have I not located the correct plug? If it is correct then what is the green wire for? The plug I found is located near the center of the dash behind the ash tray. Thanks,

asked by: Tim A

Helpful Expert Reply:

It is possible that the extra green wire you found is used for illumination. You can test that by using a circuit tester such as # PTW2993 and turning on the vehicle running lights. If it shows power then that is what it is for but aftermarket brake controllers do not use the illumination circuit. If it does not have power and all of the other wires in the harness have the right functions I would not worry about it.

It is also possible that the wire you found is the alternate brake light circuit. On some Ford trucks there is a green wire that is used to connect to a brake controller red wire when hardwiring in a brake controller. But that wire is not used if you are plugging in a brake controller.

The factory plug location on your truck is located under the dash near the center console on most vehicles. So if that is where you are looking, and it sounds like it is, it is likely the right plug.

expert reply by: Michael H