Where Does Brake Controller Red Wire or Trailer Wiring Harness Red Wire Go on 1984 Ford F-150  

Question:

Expert Reply:

On a brake controller just as # 90195 the red wire connects to the cold side of the brake switch. The brake switch, usually located above and/or attached to the brake pedal arm, will have a wire that only has power when the brake pedal is pressed. If the wire has power when the headlights or turn signals are on then it is not the correct wire. But the installation of a brake controller will not help get the turn signal to work. Is it the truck's turn signal or the trailer?

If it is on the truck then it could just be a bad bulb, socket, or wiring. It could also be a fuse or relay. If the problem is on the trailer side then it is likely a bad ground. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light but can show up any time.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

If you are talking about the red wire on a trailer wiring harness then on a trailer wiring harness the red wire usually goes to a brake light wire on the vehicle it is being installed on as long as that vehicle has separate brake light and turn signal bulbs. On the 1984 Ford F-150 the stock wiring configuration is combined meaning the brake lights and turn signals are on the same bulb.

In that situation the red wire would be grounded along with the white wire. The yellow wire would then connect to the tow vehicle combined brake and left turn signal wire. The green wire is for combined brake and right turn signal. Brown is for running/tail lights.

expert reply by: Michael H

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