How to Correct Weak Ground Connection on Vehicle and Trailer

Updated 05/25/2017 | Published 05/24/2017

Question:

I have a trailer that works sometimes and sometimes dont. The brake lights or turn signals dont even work but if I hit a bump they come on. I put some grease on the ball and try to ground the trailer to itself but nothing only if I drive and hit a huge pothole will they come on. When the did come on, they worked for a while. Then they went off once I took it off the ball. Could it be my ball is too rusty and does not have enough grease on it? my hitch has rust on it, could it be that? Its a Wells Cargo trailer.

asked by: Thomas H

Expert Reply:

A hitch ball does not make a good ground connection for trailer lighting functions. The fact that the lights work for a bit after you hit a bump with the hitched trailer tells us that somewhere in your trailer and vehicle wiring there is an intermittent ground connection. This kind of problem usually has a fairly simple fix.

I suggest you locate the tow vehicle's wiring harness ground wire. This white wire needs to be firmly attached to a clean bare metal surface on the vehicle. On the trailer the same is true for the main ground wire there. Both need to make bare metal-to-metal contact with the vehicle and trailer frames in order to give you a good ground. A weak ground may sometimes let one light function work but not another.

You can sand off the existing grounding points to remove rust, paint, primer, grease and dirt and then re-attach the ground wires to that clean surface. Apply some dielectric grease like # 11755 to those new connections to help prevent water and dirt from causing corrosion in the future.

expert reply by: Adam R