Locating and Repairing Ground Problem in Wiring of Boat Trailer

Updated 08/21/2012 | Published 08/17/2012

Question:

My boat trailer lights work fine when connected 4-pin flat to my ford pickup, but not when connected 4-pin flat to my 2012 Grand Cherokee. I have a 4-pin flat connector power tester and everything tests ok. The only difference is the hitch ball on my truck in directly connected to the bumper, whereas I have a factory installed Tow Package with receiver hitch on my Jeep. I suspect a grounding problem, or lack of ground there of. What is your opinion?

asked by: Larry

Expert Reply:

It sounds like you are on the right track with the ground problem.

Check your trailer connector on the Grand Cherokee, and make sure the white wire is grounded to the frame of the vehicle.

Even though your trailer works fine when connected to your truck, you still might have a weak ground on the trailer. It is not unheard of that a given trailer will work fine with one vehicle, but not with another.

Check the grounding point where the white wire from the connector attaches to the trailer frame, which is usually on the trailer tongue somewhere. Make sure this connection is tight and not corroded. Check the points where the lamps attach to the trailer. Trailer lamps will ground either through their mounting studs that need to be in direct metal-to-metal contact with the trailer frame, or through a ground lead that is attached to the trailer frame. If the trailer has a folding or swing-away trailer tongue, you might need to run a jumper wire from the folding portion to the stationary portion of the tongue. Over time, the folding mechanism can become loose, thus not maintaining a continuous ground connection.

Check these items for me, and if you do not find the problem, get back with me and we will look into some other possibilities.

expert reply by: Mike L