'06 2500 HD trailer wiring harness question

I'm trying to provide power to my slide in camper via the wiring harness Chevy provides which is located under the bed of the truck, toward the front
of the bed, on the driver's side. The harness has everything for a 5th wheel (turn indicators, brake controller, etc), but I only want +12V and ground. Both the manual and the label that is on the harness indicate that white is ground and red is battery. I've verified the ground (white) wire is a good ground and that the battery (red) wire isn't providing +12 volts. I checked the fuse block under the hood on the drivers side and the fuse that's labeled as "trailer bat" looks good. It's dark out and I'm tired of holding a flashlight and a multimeter. I plan to resume and/or contact the dealer in the morning, but wondered if someone here might have the answer before then.
Thanks in advance. Because I'm starting a 10 day trip some time tomorrow, whether I have power to the camper or not, I might not see and/or reply to any answers until my return. This is kind of a "shot in the dark" (pun intended) post.
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Have you checked the red wire for 12 volts with the engine running?
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wrote:

Just did, still no power, not even to the 7 pin connector at the rear trailer hitch. Thanks for the suggestion. I'll call the dealer when they open.
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Greetings,
Many times Chevy installs the wiring harness but if the truck doesn't come prepped with the tow package then the proper fuse and/or relay won't be installed. The trailer wiring harness that came with my '04 2500HD had a page of instructions that showed where to install the relay in the under-hood electrical center, but everything had already been put in place (either by the factory or the dealer) so mine was all powered up and ready to go.
If the line you are trying to get power from is the circuit for trailer brakes, then you might be out of luck because that won't get power unless you have a brake controller installed, and even then not until you have it set correctly and are using your brakes.
The other thing to consider is that on 12v systems white is seldom ground (like in 120v AC house wiring). Black is commonly the ground, but it could be set up differently for the harness because I have seen white ground wires on trailers.
You might also want to check the circuit with the truck running. It may be wired so that the trailer/camper won't draw power unless the alternator is turning to prevent drawing down the truck battery when parked. I don't have the 5th wheel harness but I believe on the 7-pin connector on the back of my truck I don't have constant power to any of the leads without the truck running. The turn leads for the turn signal, brake and running lights all have power but are all switched (not constant).
Cheers - Jonathan

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I have no power to the either the 5th wheel harness or the 7 pin connector at rear trailer hitch even when the engine is running, but all the other pins get voltage when that circuit is active (i.e. stop, turn indicator) so there is a common issue somewhere. Thanks for your help. I may just have to do without being able to charge the battery in the camper this trip.

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Apparently it wasn't connected, even though it has the heavy duty towing package. The manual didn't have instructions; it only stated that if it wasn't wired already the dealer could do it. The dealer had it wired in about 30 minutes, no charge as I purchased it for the express purpose of putting the camper on.

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Ed, enjoy your trek! Be careful and safe
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