Troubleshooting 7-Way Trailer Wiring Where Brake Lights Come On as Running Lights on Trailer

Published 03/02/2018

Products Featured in This Question

Hook Probe Circuit Tester

(70)

$14.54

Trailer Wiring Junction Box

(827)

$35.23

Ring Terminal - 12-10 Gauge Wire - 3/16" Ring ID

(72)

$1.25

Question:

It has a seven way plug for the trailer. According to wiring diagrams the plug is wired correctly. As soon as you turn the key on the brake lights come on and will not go off. The break wire which is the red one according to wiring diagrams is the one that is hot when the key comes on. How can I correct this problem.

asked by: Jeff L

Expert Reply:

The running lights should come on as soon as the running lights on your vehicle come on. This should give you a light in your tail lights, but it shouldn't be as bright as a turn signal or a brake light. If you are getting the brake light, then your tail lights have been wired incorrectly and most likely have the brake/turn light wire switched with the running light wire.

I recommend using a circuit tester like # PTW2993 to check the wiring functions at your 7-way and then check the functions at your tail light to confirm the wiring configurations. If you find they are incorrect, you can change them at the tail lights or you can change them at the trailer side 7-way plug if there aren't clearance lights also connected to that circuit.

An easy way to correct your wiring is to add a junction box like # 38656 and ring terminals # 44-5310A.

expert reply by: Jason S