Troubleshooting Trailer Wiring Where Right and Left Stop/Turn Circuits Seem to Flash Together

Question:

My trailer has recently started playing up when indicating. If I indicate right, the trailer blinkers both flash. If I indicate left, nothing flashes. Brakes and other lights are fine. I have also scrubbed the plug pins, and checked the connection of wires inside plug. Any thoughts? Solutions? Thx

asked by: Al

Expert Reply:

Sounds like there's a short between the stop/turn circuit of both sides of the trailer. So what you'll want to do is determine first if the problem is on the vehicle or trailer side of the wiring. Best way to do that is use a circuit tester like part # PTW2993 to test the pins on the 7-way for voltage in all of the right places. See attached picture.

If the voltage is good on the 7-way the short is somewhere on the trailer wiring and you'll need to trace the wiring back on both circuits to see if you can find where the two are shorting together.

Other possibility is a weak ground on the trailer wiring which causes unpredictable behavior from the lights as well.

expert reply by: Jameson C