Dim and Malfunctioning Trailer Lights on a Trailer Towed by a 1988 Chevy C/K Series Truck

Question:

I bought a brake controller and 7 pin setup from your company. I installed the t connector on a 1988 C/K Chevy pickup. I have circuit tested the t connecter and the 7 pole plug on the truck. They all function properly when tested with a circuit tester however when I connect my trailer the running lights are very dim, The left turn signal brings on all the lights and the brake lights work however when the brake lights are engaged the running lights go off. I know there is no issue with the trailer because I have a second truck that is wired to accept the trailer and I have no issues with it. Everyone works just fine. The only other information is that the trailer is a 6 pole so I also bought the 7pin to 6 pin adapter.

asked by: Nick

Expert Reply:

This sounds like a weak ground, corroded connector, or both. Make sure that the ground on the 7-Way you installed is attached to a clean and corrosion free bare metal surface. A weak ground could cause this issue. Ground problems normally show up when there is more load on the system like when the running lights are on and you step on the brake. Also make sure the 4-way that you installed is properly grounded.

A corroded connector can cause all sorts of weird things to occur as well so check the trailer side connector and clean out any dirt and corrosion.

Another possible issue is that if the trailer lights are drawing more than 7.5 amps for brake and turn signals per side and/or more than 7.5 amps for running lights it would be overloading what the 4-Way is capable of.

expert reply by: Michael H