No Taillights On Boat Trailer When Connected To A 2003 GMC Yukon XL 7-Way Connector

Updated 11/04/2010 | Published 11/03/2010

Question:

Im having trouble figuring out a tail light problem on an 03 GMC Yukon XL. Suddenly, noticed the tail lights on my boat trailer stopped working, but brake, turn signals, etc. still work just fine. Tested the pins on the 7-pin connector and the top left pin i.e. at 11 o clock does not seem to have any power now. Tested all others for brake, flashers, etc. and they are all good, so I know I had a good ground in my test, just no tail light power! Its the factory 7-pin connector and Ive never had trouble with it before. Any ideas where I should start? wiring behind the plug does not appear to have been damaged and I cant find a blown fuse. BTW - tail lights on the truck do work just fine.

asked by: George

Expert Reply:

It sounds like a blown tow package fuse in your fuse block on your 2003 GMC Yukon XL. You will need to check the accessory fuse block under the hood of your vehicle. When you remove the cover of the fuse block there will be a legend on the underside of the cover that will show the location of the fuse.

If the fuse is blown you will then want to check the taillight wiring on your boat trailer for any pinched or frayed wires that could be shorting out on the trailer frame and causing the fuse to blow. You will want to repair or replace those wires. I am sending a link to a page of the 7-way trailer wire harnesses.

If the fuse is not blown you can test the wires going into the back of your factory 7-way connector on your vehicle and find the wire that is for the taillights (usually brown). Test the taillight wire to see if you have power going into the 7-way. If you have power on the taillight wire going into the back of your 7-way and no power coming out , then the 7-way connector would be the problem. You can replace the factory 7-way with the Hopkins 7- and 4-Pole Trailer Connector # HM40975.

If there is no power on the taillight wire going into the back of the 7-way and the fuse is good, you will then need to trace that taillight wire on your vehicle to determine where the problem is on that wire.

expert reply by: Jeff D