Trailer Running Light Pin Shows Only 6 Volts on a 2008 Chevy Silverado

Question:

2008 Chevy Silverado 2500HD LTZ 6.6L Duramax with Allison Trans. What I have is everything on the trailer works except the running lights non of them I used a multi meter and it shows 12 for the power and only 6 for the running light prong off the truck. Should that also be 12?? The truck running lights work if it matters.

asked by: Jack F

Expert Reply:

You should be getting 12 volts on the running light circuit when the running lights are turned on in your 2008 Chevy Silverado. Something is preventing the full voltage from getting to the trailer connector.

The first thing I would check is the trailer connector on the truck. Make sure it is clean and free of corrosion inside where the wires attach and outside on the pins. Checking the inside of the connector is critical because corrosion could build up in there and you would not necessarily know it.

Also inspect the wiring as much as you can and fix any broken or pinched wires. It is not likely a fuse or relay for the tow package wiring because there is some voltage getting through to the connector indicating power is flowing. Sometimes though if a relay is bad it will still allow power to go through, just not enough to operate the lights.

Just to cover all the bases it also would not hurt to inspect the trailer wiring and connector. The main trailer connector ground and the light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H