Trying to wire my slide in camper to run off my truck and charge camper battery from truck. The camper has its own set of turn/brake and running lites and I need to hook them to the trailer lites of the truck.

check for camper wiring and trailer plug connections

If you are referring to a camper, the 12 volt auto battery powers them. Fully charge the battery first. there is a switch inside the camper to power the motors be sure its turned on. A lot of campers seem to have a problem with poor wire connections and broken wires. clean all connections check for broken wires and check fuses. good luck.

I think you either have a defective bulb socket or you still have a ground problem, that is the only thing that can cause this, the ground issue may be caused by the turn signal switch as well.

Take it to an automotive electrical place , It won't cost much.
It's kind of a pain to do it your self. you have to lay under the truck and probe several wires and tap into them , and get them all right.
Most larger campers will have a 7 pin connector. 12 V for charging the battery , lights , brakes and reverse if the camper hides your truck lights , electric brake (not used) , ground ,

carry an extra altenator just in case for your truck

Call dealer & ask them to run your vin# to see if it came with towing package. They shouldn't mind. If not, you'll have to wire it in yourself.

Hey Paul, it's most likely a wiring problem. There is one wire designated for just the running lights. What type of plug does the truck have? Probably 6 or 7 way (6 or 7 wire). You can check the plug-in at the truck with a multi-meter to see if there's power at that point. If there is, then the problem is somewhere from the trailer plug to the lights on the trailer. If you have a 7 way plug, the center plug is for aux. power (back up lights on what you pull, if equipped). One wire is power to the camper battery for a breakaway switch, one for left turn and stop, one for right turn and stop, a ground wire, one for running lights, and one for trailer brakes. To determine what wire does what, 1st with meter check volts of all wires w/ truck and trailer hooked up, truck running, power wire to battery for breakaway should show voltage if equipped w/ a trickle charge, brake wire will show low voltage, approx. 2 volts, apply brakes and should go up to approx. 12 volts, put on L turn signal, meter should go up and down, as power to blinker pulses on and off, do the same to determine which is the R turn signal (put foot on truck brakes will show voltage to brake lights AND brakes, continue w/ process of elimination to determine which is running lights, and exactly where power is not going.

The extra battery is there because of the glow plugs and intake heater of the duramax. During cold weather both of these systems draw high amperage from the batteries. A single battery will function, but not as well as a pair.

The two wires running the length of the truck are most likely a 12volt pwr supply,a ground or trailer brake signal wire.usually for charging a camper trailer battery and trailer brakes, check the brake lamp fuses in your fuse centre,most likely 10a.replace if open.if they still are inop,check with a test lamp to see if pwr is at the light sockets,(clamp of test light to good ground,usually white wire for brake)if no pwr is there then make your way to where the trailer plug was installed and check for pwr there(make sure your brake peddle is depressed during these tests,with key off as not to pwr up the park lamps)also check the ground at the same time(usually black)by reversing your test lamp(clamp to 12v)your brake switch could also be faulty(switch with button on arm of brake peddle).pick up a chiltons or haynes service manual to help with wiring diagrams and wire colors.

The other is a 12v supply to charge the TT battery. I had to run off the battery w/inline fuse. Did you install a relay? my battery keeps gettin drained from my prodigy brake controller.