Both Turn Signals Blink On Trailer When Brake and Signals are Applied at the Same Time

Updated 10/14/2011 | Published 10/13/2011

Question:

1997 dodge 2500 has round 6 plug oulet. trailer has 4 wire plug. when i hooked it up, the tail lights, brake lights, and turn signals they worked individually ok but when the brake lights and turn lights were used at the same time, both turn lights flashed. What is happening ?

asked by: Mike B

Expert Reply:

The first thing I would check is the trailer side and vehicle side connectors for any dirt or corrosion and clean it out. That could cause a short circuit situation. I would then move on to checking the grounds on the trailer. The main ground should be connected to a bare metal surface on the trailer frame.

Most trailer tail lights ground through the mounting studs unless there is an obvious ground wire. In either case, you will want to make sure the grounds are attached to clean, corrosion free metal surfaces on the trailer. Another thing that can cause a bad ground is a plastic license plate holder on a tail light that grounds through the mounting studs.

You can also check that the adapter you are using matches how the truck 6-Way is wired. On the # 37325 adapter that you have referenced, if you are looking at the face of it the pin in the 12 oclock position is running lights, the pin at 5 oclock is for right turn and brake lights, the pin at 7 oclock is for left turn and brake, and the pin at 11 oclock is for ground. If you find your truck 6-Way does not match this you will have to re-pin either the truck 6-Way or the adapter so that they are compatible.

expert reply by: Michael H