Troubleshooting No Trailer Lights Working But 7-way Connector On Truck Working Correctly

Question:

I have a 2005 GMC Sierra with tow package. I also have a 1998 Forest River Salem travel trailer I inherited. I was hooking it up yesterday and had all lights working except flashers yes even brake lights worked. I wiggled some things, disconnect the 7pin plug to put more connection grease on it and plugged it back in. Now I have no lights. Truck side tests fine with the multi-meter. Where do I go from here?

asked by: Brent R

Expert Reply:

Since the you verified that the 7-way connector on your 2005 GMC Sierra is working properly that narrows the issue down to somewhere on the trailer.

Now since none of the lights are working it is more than likely the trailer connector. Check for any corrosion and or debris in the trailer side connector that would cause a connection issue.

When you say you wiggled some things, would that happen to be the junction box where the 7-way connector gets connected to the trailer wiring?

If so I would check for loose/bad connections in and near the fuse box that may have come loose.

If this does not fix your issue just let me know what you find and we can go into more in-depth trouble shooting.

I included a link to a helpful article on wiring for you to take a look at.

expert reply by: Samuel C