Cabover camper wiring with both camper prep (VYU) and 5th wheel prep (CMT) packages

shanek · July 21, 2022

I had a 2021 Silverado 3500 HD with the snow plow prep / camper package (VYU). There was a wiring harness zip tied up under the rear of the bed on the driver’s side available (intentionally) for connecting a cabover camper wiring harness to.

Fast forward a year, I now have a 2022 Silverado 3500 HD (long story), but not only with the snow plow prep / camper package (VYU), but also with the gooseneck / 5th wheel package (CMT). The later comes with the 7 wire receptacle in the bed (intended for gooseneck/5th wheel hookups) which of course makes sense. However, the loose wiring harness under the bed for the camper prep is nowhere to be found so far as I have been able to tell. Yes, one could utilize the in bed 7 wire port/receptacle, but this is not desirable for at least three reasons.

1) there just isn’t the physical space. Yes, tonight I did it as I’m leaving tomorrow and needed something, but it involved removing the entire housing from the 7 wire plug leaving only the physical connections exposed and then using a nonconductive probe to push the remaining part of the plug (with no housing) into the receptacle as far as I could. It seems loose and I expect it to fall out. The wires have just enough space assuming the camper doesn’t shift.

2) this doesn’t cleanly facilitate a means to hook up a battery isolator which I’d much prefer to do. Granted, I could still do this but now I have wires going multiple places. I also don’t want to use the 12v power connection in the trailing plug as I’d prefer to run a larger gauge wire direct from the battery to my isolator to my camper receptacle to the camper.

3) utilizing this receptacle, the truck thinks that there is a trailer connected (I also have the advanced trailering option) and causes required interaction with the in cab HMI.

Yes, I can get it done and make it work enough for now, but this doesn’t seem to be optimal and wouldn’t think what GM/Chevy intended. Is there a wiring harness associated with VYU I’m not finding that can be used for the camper or did they really intend for me to utilize one of the “trailering” ports (essentially CMT) which just seems really odd and uncool?

I’m sure I could find an adapter from eTrailer to split one of the trailing connections under the bed for use with a cabover camper and my camper harness/plug/receptacle, but again, the truck will think this is a trailer, which is incorrect.

jhplak325 · July 21, 2022

The snow plow prep/camper package does not include the trailer wiring provisions for 5th wheel/gooseneck, that is a separate $35.00 option when ordered from factory.

Your only option would be to pick up a splitter like you are thinking.

shanek · July 21, 2022

I think that would be trailing wiring provisions (UY2) which is not a compatible option with the gooseneck prep package. The later has the trailing wiring to the inside of the bed, but doesn't so far as I can tell have a non trailering harness loose under the bed intended for use with campers. It seems the option is to get a splitter and then deal with the truck thinking the camper is a trailer.

Or, thinking about it, I bet if I pull power and ground from a different source as I was planning (not using the power and ground from the "trailer" cable bundle) that the truck then wouldn't think there was a trailer attached. Thank you for allowing me to talk this through myself.

Edited July 21, 2022 by shanek

Another JR · July 21, 2022

I have a slide-in camper that is bed length and does not hide the truck tail lights. I initially ran my camper’s clearance lights from the trailer harness using a splitter, but very quickly decided I did not like the effects of the truck detecting the camper as a trailer (defeating the rear park assist). I switched to running those lights off of a splice into the harness for the left rear fender marker lamp. If I decide to return it to factory configuration I just need to replace a two foot long two wire harness.

If your camper hides the tail lights you probably want to use the trailer harness for the light connections to the camper despite the truck seeing it as a trailer. The rear park assist is useless in that case anyway.

The trailer harness battery charging wire is only 10 awg. That’s fine for maintaining the charge on a brake system safety battery, but for charging large camper batteries at a high current, you probably will want to run separate large fused cables from the truck battery to the camper. How large depends on your power system. I used 6 awg to a Victron Orion 30 amp dc to dc charger located in the camper battery compartment. I have a 200 ah lithium battery in the camper. People running lead acid batteries often direct connect the batteries to the truck via an isolator with much larger wires.

I’m happy to help if you have more electrical questions, but I’ll stop now in case I’m telling you stuff you already know.

shanek · July 22, 2022

Yes, the camper hides the tail lights. If I understand you correctly, procuring a splitter for the trailer harness and only using the clearance, turn(brake) and reverse leads, and not the power leads, the truck will still think a trailer is connected? It must be measuring resistant or voltage drop or something then. Foo.

Yes I agree with not using the 10 awg battery charging wire in the trailer harness for camper power/battery charging and was planning to run a 6 awg direct fused connection from the battery to my isolator, etc. as you detail. I didn't do that last night just as a temporary thing for the next week, but agree with you that is the way to go!

Cheers!

Another JR · July 22, 2022

You will want to run 6 awg positive and negative wires for charging rather than relying on the trailer harness ground or body connection via the hitch.

All I had connected to the trailer connector was the marker lamps and the truck detected it as a trailer. You could splice into all the light circuits to avoid that but If it was me I wouldn’t want to alter the truck wiring that much.

If you decide to use the trailer circuits, Curt makes harnesses that just insert into the connection at the bumper or 5th wheel connector. They make them in 7 and 10 foot lengths.

Curt 56000, 56072

shanek · July 22, 2022

Understand on all... Frustrating that there doesn't appear to be a clean option for wiring the needed lights for the camper. I agree with you not wanting to alter the truck wiring and even if I did the computers in the truck would probably take issue with that as well. Interesting that GM/Chevy doesn't think one might want to run a cabover camper in the summer and pull a gooseneck trailer for work at other times.