Auxilary Power '03 GM

My '03 HD has the factory 8 wire RV plug at the receiver hitch, but I can't detect any 12v power through the plug. From what I read in the owners manual it leads me to believe all the things are in place for it to be functional, but that you must do something to either connect it or turn it on to make use of it. Its not very clear about it, only that it has the capability built in.

I checked with my local GM dealer service managers about it but they weren't much help, didn't really seem to understand my problem. One service tech seemed to understand and actually showed me on an '07 where the wire was bundled and tied, and the "stud a" in the underhood fuse box that it needed to be connected to. I thought that would solve my problem, but when I got home and checked mine I could find neither the wire bundle nor the place to hook it like the '07 had.

I know its all there somewhere, it has the heavy (red) power wire coming out of the harness and going into the back side of the trailer plug. I did finally find in the electrical index which fuse is for aux trailer power and checked that it is in place and good.

Anyone of y'all dealt with this before for your travel trailers? I'd really like to solve it myself rather than check the truck in the service department a la $90 an hour.

Link

Thanks again for the great info. It saved me time, frustration and probably money too.

Its all a lot easier to do since the controllers went electronic. Its an all wire hook-up instead of having to run wire everywhere and even splice into the hydraulic brake lines like the old days.

Its has to be the "40A B+ Trailering J-Case Fuse". It was never put in place when the brake controller was installed.

Hey thanks for the great information, with lots of pictures no less! I'll have to save that page.

just for info the 07 has 2 wires bundled under the hood for this. If the factory installed the trailer plug the wire you need is under the master cyl. If its a after market there is another wire bundle in-between the battery and the fender well. Maybe thats where it is on the 03. Ya need a flashlight and a 3 jointed neck to look there but maybe ya might get lucky.

Don't know about an 03 but some years had a dummy fuse that you had to replace. Looks like a real fuse just don't do nothin

If I have to go to the trouble of running wire, I'd go on and run 2/0 welding cable and a large plug to tie both batteries together for more winching power.