cdru

2014 xlt 4x4 with trailer brake control on dash. Will the camper draw off the truck battery if left plugged in while camping? Is the truck wired to only charge the camper and not draw off the truck? Thanks, cdru

Gene45

On my 2012, there is no voltage on the7 wire plug unless the engine is running, So, no it won't. There is a relay under the hood to prevent that.

smokeywren

Not unless you have the truck ignition key turned on. With the key turned off, the truck battery is not connected to the trailer battery, even though the trailer wiring plug is connected.

On my 2012 Lariat, the trailer lights will not work unless the truck lights are turned on, but they will work with the key turned off.

So not much danger in running the truck battery down while camping, unless you are dumb enough to leave the truck lights on or the truck ignition key turned on and engine off while camping.

Not my area of expertise, but here's my guess: With the key on and engine running and trailer plug connected, the trailer battery will draw current from the truck battery only when the trailer battery has a very low state of charge, and the altenator is not putting out enough amps to charge the trailer battery in a reasonable time. But kill the engine and leave the key on with an almost-dead trailer battery, and the trailer battery will suck power from the truck battery.

smokeywren

I'll be picky, picky.


With the key off, there is no voltage on the 12-volt hot pin used for trailer battery charging. So no, it won't.


But if the truck lights are on (tail lights, running lights, brake lights, turn signal lights) there is voltage on the three pins that supply juice to those lights, even with the key turned off. Or at least that's what my trailer emulator reports for my 2012 Lariat.
https://www.etrailer.com/Wiring/Tekonsha/6562.html

stormrider151

Now I'm confused. When I purchased my trailer the service tech that did my PDI said to either leave the truck running while the trailer was plugged in or remove the plug from the truck when it is parked and not running. Interesting.

smokeywren

I cannot imagine why he would say such a dumb thing, unless he was not familiar with late-model F-150 trailer plug wiring. While traveling cross country, we almost always overnight in an RV park, and we rarely disconnect the truck from the TT. And we don't disconnect the trailer plug unless we also disconnect the hitch. So we have had numerous nights of experience when we broke his rule, with no adverse effects.


However, if he was giving his generic speech instead of customized to a late-model Ford, then he may be right. Lots of folks wire their own trailer plugs, and include a hot wire direct from the battery to the 12-volt hot pin on the 7-pin plug. For those folks, leaving the plug connected overnight could result in a discharged truck battery the next morning.

cdru

When we had our Dodge truck the owners manual said to disconnect the trailer as it was a direct connection and would run down the truck battery. I was wondering if the our new Ford was the same. Sounds like the Ford has a better setup and will isolate the truck battery when parked. Thanks for the info. cdru

Ron AKA

My older Ford keeps the truck battery connected to the trailer even when the truck is not running, or key on. No idea on the new ones, but get a connector wiring drawing and just check the voltage. In my opinion it would be unfortunate to not have the truck be able to power the trailer. My standard practice in a campground where we do not have AC power is to plug the trailer into the truck so the truck battery helps with the trailer load. I depend on driving the truck enough to keep the battery charged up, and I suspect the truck battery will transfer to the trailer battery to help keep it up too.

stormrider151

Not long after I got my 2012 screw, I had to take my TT in for service. When I went to pick it up a week later the battery on the trailer was dead. The hot lead had no power to it. Not a good situation for the brake away switch with a dead battery. A service tech ask if the truck was new. When I said it was he took a fuse from the glove box and installed it into the high power block under the hood. Then the hot lead had power to it. I guess I need to put a meter on the hot connection to see if the is power to it with the ignition switch off.

seaeagle2

Old school, my 77 F250 had two batteries and an isolator, one was wired to my camper and the other was the truck battery. you could run the camper batttery dead and still have a battery to start the truck.