I just piced up a new truck camper for my rig and now wondering what is the best way to hook to the 12v system? I have the dual batt. but which is better to hook to? Any leads/ideas thanks in advance.

I ran a pair of #8 stranded wires from under the hood to a socket in my truck bed for 12volt power to the camper. One wire was for a reliable ground and the other was through a relay (with a circuit breaker in the line) that was controlled by the ignition switch. The idea was to allow the truck to charge the camper battery while driving but not ta allow the truck's starting batteries to become discharged while stopped. Lights, fridge,heater fan, etc. could kill your starting batteries over night while stopped along the way. For my running lights & backup lights, I just picked them out of the trailer socket wiring harness down under the truck bed below where I installed the socket in the truck bed.

The truck batteries are wired together, so you can't hook up to just one battery. Besides, the truck batteries are not meant for long continuous use like a deep cycle battery is. You might want to get a third battery for the camper only. You could also replace one of your truck batteries with a deep cycle (like the yellow or blue top from Optima) and disconnect it from the truck when using it with the camper. Be advised though, replacing only one battery is not necessarily recommended.

I have heard that using the OEM trailer 7 pin wiring will work to run a charge to the camper battery any one ever tried? In the facotry setup there is a charge line in the 7 pin all that needs to done to activate is adding a 40A fuse under the hood?

I also was wondering if i run a charge ogg the 7 pin what gage wore should i use from the 7 pin to the camper battery?

You may consider asking around at the forums on www.rv.net.

just set up the wiring for my fifth wheel which is coming. Brake controller went in ok but the wiring for the fifth wheel has a problem. The wire for the brakes was miss labled (that was easy - it was the other big one). I have trouble with the lead from the battery. The wiring harness label for the brake controller and the owners manual said to discard the 40a fuse and not install it if I have dual batteries (TP2). I don't have option TP2 but I do have dual batteries. The battery lead at the trailer connector wiring harnes is not hot unless I put in the fuse. If I put in the fuse the wire is always hot so I could discharge the batteries overnight. Seems to me that if the ignition is off the battery lead should not be hot. Whats wrong here??

have a 2005 2500HD

just set up the wiring for my fifth wheel which is coming. Brake controller went in ok but the wiring for the fifth wheel has a problem. The wire for the brakes was miss labled (that was easy - it was the other big one). I have trouble with the lead from the battery. The wiring harness label for the brake controller and the owners manual said to discard the 40a fuse and not install it if I have dual batteries (TP2). I don't have option TP2 but I do have dual batteries. The battery lead at the trailer connector wiring harnes is not hot unless I put in the fuse. If I put in the fuse the wire is always hot so I could discharge the batteries overnight. Seems to me that if the ignition is off the battery lead should not be hot. Whats wrong here??

have a 2005 2500HD
You don't have dual batteries if you have a diesel you have tandem batteries (both batteries hooked together). Read your Diesel supplement manual. Dual batteries (seperate circuts) are only in gas motors.