12V charging/aux line in trailer connector

[Ironring1]

Hello, all. I have just rewired my (used) pop-up trailer for the 7-position circular connector on my Envoy. Everything is working perfectly, except for the 12V charging line for the trailer's battery. Turn signals & running lights are fine, so it is not a ground issue. I've measured the voltage at the 7-pin connector, and at the connector that actually plugs into the rear of the connector (behind the bumper) - 0V in both cases. I then opened up the fusebox under the hood and checked fuse 32, which tests fine, and I was able to measure 12V at the input side of this fuse's connector (the side furthest from the front of the vehicle). So, somewhere between the output post of the fuse and the connector on the rear of the truck, I have a broken line somewhere. Can anybody tell me how the harness that runs to the rear of the truck is routed (both on the underside of the truck's frame and inside the engine compartment) so that I can find the break?

Thanks,
-Chris

 

[Texan]

Look for the thread about the "famous" red wire under the hood, near the battery.
I can not link to it.

 

[Ironring1]

Brilliant! It never occured to me that that line would not be connected by default!!! Also, my owners manual makes no mention of it I found the red wire with ring terminal, verified that it connected to the rear trailer connector, verified that the cold side of the fuse connected to teh stud, and bing bang boom, my trailer is powered. Thanks for the quick reply; I love this site

-Chris

 

[The_Roadie]

My best guess, and I tow that kind of trailer, is that the BEST design would be to use a wire that's hot during RUN mode to close a relay to connect the fused threaded stud with the trailer feed wire. That way, a connected trailer won't be running the battery down overnight if you have the trailer fridge running on 12V and drawing 10-15A constantly, and stop at a roadside trailer park and leave it all connected. GM's not going to install a relay for the rare RV owner, but there's no excuse for the incompetence of the manual writers who couldn't be bothered to say ONE WORD about the red wire with the mystery ring lug. Shame on them, I've been saying for ten years.

 

[IllogicTC]

My best guess, and I tow that kind of trailer, is that the BEST design would be to use a wire that's hot during RUN mode to close a relay to connect the fused threaded stud with the trailer feed wire. That way, a connected trailer won't be running the battery down overnight if you have the trailer fridge running on 12V and drawing 10-15A constantly, and stop at a roadside trailer park and leave it all connected. GM's not going to install a relay for the rare RV owner, but there's no excuse for the incompetence of the manual writers who couldn't be bothered to say ONE WORD about the red wire with the mystery ring lug. Shame on them, I've been saying for ten years.

A relay would be a nice way to have automation, or you could always just work out a manual switch to the same relay rather than feeding off RUN if you'd like to feel "in-control" of the power plug.

 

[Black08TB]

I just hooked up the Red wire to my under hood fuse box today. I tow an 18' Maxum bowrider boat with the TrailBlazer, during the summer months boating requires the use of our two person towable raft. My 7 tab - 4 Way Flat converter for the trailer has a cigarette lighter plug built into it. I bought it figuring I'd use it to plug in a 12v vacuum (can be reconfigured to pump air as well) and inflate the towable with out the doors opened and using the cigarette lighter in the dash or rear console. I had no idea that the 12v power out back wasn't tied into the fuse box by design. Been scratching my head for a few summers off and on wondering why I didn't have power to that tab in the trucks trailer wiring socket. The fuses were where they were supposed to be. I just bought a Chilton manual for it last week and couldn't find a mention of the issue. I found this thread last night and made it work today. No need for a relay for my use, it can stay "Hot" all the time.

This site is alright, thanks guys!!