Trailer Lights Are Dim and Not All Trailer Light Functions Will Operate at the Same Time

Question:

Running lights work but brakes an turn doesnt work when running lights are on and when running lights are off the brakes and turn work but very dim. I just upgraded to led I ran new brake wires and got a new 7 way harness . I ran good ground from battery to harness . Dodge ram 1500 4x4ext cab 4 way to a 7 way , 1987 terry 20ft trailer 7way plug

asked by: Brandon N

Expert Reply:

The most common cause for dim trailer lights and/or only some trailer lights working is a bad ground connection. If your ground connections are bad, they may pass only enough current for some of the lighting functions to operate, but will not pass enough current for all light functions to work at the same time.

You need to ensure a solid ground connection both at the vehicle side and on the trailer. Since you have
run a vehicle-side ground directly from your trailer connector to your battery it is likely that the issue may be in the trailer wiring. Check for a solid ground connection (to clean bare metal) on the trailer side connector. Also trace all trailer wiring from the connector through to the lights to check that none of the wires are pinched, rubbing against the trailer frame or have worn insulation. Even a small crack in the insulation could cause the problem you are experiencing.

If you are using adapter plugs make sure that all contacts are clean and free of corrosion and that all connections are solid. We suggest an application of dielectric grease such as # 11755 to protect contacts. You might also want to refer to the linked troubleshooting article.

expert reply by: Adam R