Diagnosing and Repairing Poor Ground Connection on Trailer

Updated 03/03/2014 | Published 02/28/2014

Question:

put headlights on then nothing works. turn off lights and everything works

asked by: Vinny

Expert Reply:

Everything works okay until you activate the running lights and draw maximum amperage through the system. This is the classic symptom of an insufficient ground connection.

Find the main grounding point on the trailer by tracing the white wire from the trailer connector. This wire will usually ground to the trailer tongue. Make sure this connection is tight and that the connection is not corroded. Then check the ground connection for each of the trailer lights. Trailer lamps can ground in one of two ways, either by a separate ground wire from each lamp that attaches directly to the trailer frame or through the mounting hardware being in direct contact with the trailer frame. If these connection points are loose or corroded, tighten and clean as needed.

If your trailer has a folding or tilting tongue or a folding bed, the pivot point might be slightly worn to the point where a good ground connection is no longer being maintained. You can simply take a length of wire with a ring terminal like # 44-5310A on each end and join the moving portion of the trailer to the stationary portion. This would maintain a continuous ground connection between the trailer tongue and the lamps.

If you have an aftermarket trailer connector installed on the vehicle, make sure its ground connection is securely made, preferably to the vehicle frame. Make sure this connection is not corroded.

expert reply by: Mike L