Troubleshooting 12-Volt Accessory Circuit on 7-Way Trailer Connector of 2003 Chevy Suburban

Question:

In the socket on the back of the Suburban I dont have +12 volts on the pin with the large red wire going to it, the one at 1 Oclock looking from the back. Your drawing of the 7 way plug shows a black wire but mine is red and reverse is not purple but it works. All other pins have the right signals and all trailer lights work. Ive checked the pin with the engine off and with it running. Ive searched the fuse boxes for a bad fuse but found none. Ive ordered a couple of trailer plugs and some lighting from you and I hope to be able to make them work when they arrive but Im stumped. I dont have a wiring diagram to trace the wire to its source, can you help?

asked by: Jim B

Helpful Expert Reply:

The differences in wire color that you found do not surprise me. Wire colors used can vary greatly, even among vehicles of the same model year.

The fuse for the 12-volt accessory circuit is located in the power distribution box under the hood, as shown in the photo I have edited for you. If the 40 amp fuse is in place, it is not blown, and the connection shown in the photo is attached, then there is a problem in the circuit somewhere between the fuse box and the 7-way.

If you want, you can simply simply make your own run to the battery. You would sever that red wire that feeds the 1:00 pin, use a butt connector to attach a length of 10 gauge wire # 10-1-1 and run the wire up to the battery through a 40 amp circuit breaker like part # 9510. This will provide you a circuit protected 12-volt feed to the 7-way.

expert reply by: Mike L