Tow a car trailer with truck camper on

No idea why camper makers think a TC needs a 7-pin plug. I use a flat-5 for the TC (same as a 4 but it has reverse light wire).

From etrailer.com I bought a truck-side plug that has both the 7-pin and the flat-5 plug (flat-4 available too). I rewired the TC to take the flat-5. The TC had a 6-pin round plug and to make it worse the plug came out of the camper all the way at the front of the camper. Somebody was drinking on the job when they engineered this.

My TC wires now exit the TC at the back of the camper since the back of the camper is located at the back of the truck, and all the truck wires come out of the back of the truck. Old-timers would call this the business end. Furthermore the factory TC plug location at the front gets hidden as soon as the TC is lowered into the bed, putting it at the rear makes it always accessible.

This would be a good time to fix the dumb things they did to you from the factory…

bonus: while I was at it I also wired a 3-prong shoreline extension to exit the TC at the rear and under the floor (same as the running light wire). This way I can plug into to electricity without an electric cord having to come out of the side of the camper. This cord is just long enough to hang down to access. When it rains, this means there is no open hole on the side of the camper. Also, I can leave my camper plugged into the extension cord that runs to the front generator which is on a front receiver hitch, while driving down the road.

I will add that this is just a short extension cord, I can plug/unplug it into the actual camper umbilical by opening the access door. So, this short cord will not be live necessarily if I power my breaker box with the inverter. I shortened the camper umbilical to about 4 inches, so I keep the cord separate. works for me. since I usually am boondocking.

You can get a round 7 to flat 4 pin adaptor at Uhaul or Harbor Freight

Make a splitter for the 7 pole, allowing both the TC and trailer to be plugged in.

And yes, you could make a 4 to 7 for your TC lights to operate.

Just get a 7 prong splitter and plug both in and go.

7 way splitter

I'd be much more concerned about the fact that you likely don't have enough payload to deal with the tongue weight and the camper at the same time.

When I had my truck camper, I installed a plug in the box like a 5th wheel uses for my truck camper. I could have, presumably, used the 7 pin on the bumper for a trailer. With that said, I had zero payload left for any tongue weight, so short of having a DRW 3500, good luck, especially with a 3/4 ton where you're already limited on payload.

I don't know about buying one but would be easy enough to make, any rv or auto parts store would have the 7 pin receptacle and 4 pin plug. Make sure the 7 pin is solidly mounted to the truck chassis or box.