""I'm assuming since the OP has a Duramax there is a second battery installed and the fuse is not needed like it is with the gas engine Silverados. It also appears that the charge wire is only energized (somehow) when the tow/haul button is on or when the headlights are fully on (not just the DRL's)...it is not a constant hot 12V. ""
Yes, my truck (Duramax) has 2 batteries. I'm pretty sure the hot wire is hooked up to the correct stud as I watched 2 different guys from the RV shop check it for the correct connection. They seemed to know right away what to look for.
I know there is a button at the end of the gear shift that sets the tow/haul, but I don't think it make a difference regarding getting power back to the plug/battery on the RV. I'm not sure. I will have to try that. It seems like the hot wire from the battery is a direct shot and not sure if there is a relay in between somewhere.
The RV tech in Tucson thought about the DRL as well and had me turn on the head lights when checking for power at the plug, so it didn't seem to make a difference. I will double check that.
