Troubleshooting a 5th Wheel Trailer with Strange Tail Light Behavior

Updated 10/25/2011 | Published 10/24/2011

Question:

I bought a new 5th wheel trailer, when I hook up to it the left brake light comes on , on the pickup and trailer, also left blinker will not flash. When I unplug the trailer my pickup is fine. I just pulled my other travel trailer and it is fine, all lights work correctly. The RV dealer says my pickup is the problem, I am not sold on that idea yet. Any advise would be great. Thanks

asked by: Ross A

Expert Reply:

To me it sounds like the wiring of the trailer connector that is on the trailer is the problem, I have had similar bizarre behavior like that with trailers and it turned out to be that circuits were getting shorted to each other and it made the tail lights behave strangely.

I would recommend that you take a look at the trailer side connector and look for corrosion and loose wiring and fix as necessary. You may also want to check to make sure that the connector has the correct pin placement and that all of the circuits are in the right locations. Check out the picture I attached that shows how a 7-way is traditionally wired.

I also attached an faq article on trailer wiring for you to check out also that you may find helpful.

expert reply by: Jameson C