Green and Yellow Wires on Trailer Wiring Harness do Not Show Any Power

Updated 08/01/2013 | Published 07/31/2013

Products Featured in This Question

20 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 30" Ground

(331)

$14.35

Hook Probe Circuit Tester

(60)

$13.03

Question:

There is a good ground on the trailer the brown wire also has good flow. But the yellow and green ones dont why would that be

asked by: Bo W

Expert Reply:

There are any number of reasons that you are not getting power on the green and yellow wires. If this is on the trailer side, the first step would be to test the vehicle end 4-Way trailer connector to see if power is at least getting to that point.

Use a circuit tester like # PTW2993 if needed to test the 4-Way end on the vehicle. If the power is not getting to the 4-Way that means the problem is on the vehicle side. I would need to know the year, make, and model of the vehicle and if the wiring on it is factory or aftermarket. Some likely causes would be fuses or relays on factory wiring or a bad converter on an aftermarket harness.

If the power is working on the vehicle side, then the issue is on the trailer. Start by making sure the trailer connector pins are clean and free of corrosion. Then make sure the main trailer connector ground is attached to a clean and corrosion free bare metal surface. Then check the grounds for the lights and make sure they are also connected to clean and corrosion free bare metal surfaces.

I have included a couple of FAQ article links that should also be helpful to you.

expert reply by: Michael H