This would give you manual control and make it much easier to access and remember to do it.
I need to climb under the truck and show you how to test the 7-pin connector. I want to turn this to the DC range right around the 20 V mark. The multimeter I got is just the cheapie from Home Depot years ago. To have an accurate test, make sure your truck has been off for at least 15 minutes before checking for power. Some trucks shut off the power, but only after a delay. If you don’t have one, you can use a test light. The first thing you’re going to need is a multimeter. So the best way to determine if your truck is always on is to just test it. However, the same principles are going to be applied to any vehicle with a 7-pin trailer connection. Since I’m talking about truck campers, travel trailers, and 5th wheels, I’m going to limit this discussion to the three major truck brands, such as Ford, GM, and RAM. The 7-pin connection provides brake lights, directionals, marker lights, and power for your camper.
This can become a bigger issue for people with truck campers because most of their time they’re plugged in in the bed of the truck. However, in most cases, the two systems are connected through the 7-pin cable that goes between the truck and the camper.
Ideally, the truck and RV batteries would be completely separate, each having their own charging source. And in your camper, there’s a battery that powers your fans, your lights, and possibly an inverter. The truck relies on the battery to start its engine and run all of its accessories. Your truck and camper are going to have their own independent batteries and charging systems. Whether you have a truck camper, a fifth wheel, or a travel trailer the 7-pin connection is pretty universal between the camper and the truck. It’s also going to damage your truck’s battery and shorten its lifespan. At its best, this situation could put a damper on your camping plans, and at its worst it could leave you stranded somewhere.
They woke up in the morning to a dead battery in their camper and their truck. Recently I received an email from a couple that had this very problem. Potential Issues If you Don’t Have A Battery Combiner