Trailer Right/Left Blinker Come On Together and Right Side has Constant Power in Trailer Connector

Updated 06/26/2013 | Published 06/25/2013

Question:

when i signal left why does right and left signal light go on on the trailer 05 gmc sierra. also i tested the wires and there is constant power on the right wireharness

asked by: Abe K

Expert Reply:

It sounds like there is a combination of issues that are causing the problems you are experiencing. Regarding both blinkers going off together when you engage the left blinker, this could be a bad ground. Bad ground connections can cause all sorts of weird problems.

Make sure that the truck side and trailer side connectors are properly grounded to clean and corrosion free bare metal surfaces. The truck ground is probably tied into the harness that leads to the connector so no worries if you cannot get to it. You will also need to make sure that the grounds for each of the lights are attached to clean and corrosion free bare metal surfaces.

The constant power draw can also be adding to the problem. The most likely cause is corrosion in the trailer connectors. Clean the pins on the truck and trailer connector but also check where the wires attach inside the connectors and clean there too. Corrosion in the connectors can cause a short leading to power draw on a pin that is not supposed to be drawing power.

expert reply by: Michael H