I have the Max Trailer Towing Package with the integrated brake controller and the 7 pin plug. Can anyone tell me if my setup includes a battery isolator? I'm hoping that the truck charges the trailer's battery but that the trailer can't discharge the truck's battery. I've read the manual and Ford's towing guide, but haven't found any answers.

 

Yes it does, but you have to make sure the fuse and relay are installed. Sometimes it's installed, sometimes it's in a plastic bag. Usually if you have the trailer brake contoller, it's installed. There's a post on it, I'll see if can find it.

 

The 7-pin wiring harness includes a battery charge/auxiliary power circuit, it is the pin at the 2 o'clock position as you look at the connector on the truck (red or red/black wire).

To enable this circuit, the relay needs to be installed in position #9 and the 30 Amp fuse installed in position #21, in the power distribution box (fuze box) under the hood.

The relay and fuse are shipped in a plastic bag, usually in the glove box and unless your dealer installed them as part of the vehicle prep, you need to do it yourself. I have the TBC, and my relay and fuze were in the glove box.

But you knew all that, so to answer your real question, I don't think there is a battery isolator. So there is a possibility that you could discharge the truck battery if you leave the trailer hooked up and are using something in the trailer that runs off the battery charge circuit.

That's the only reason I can think of, why they don't automatically install the relay and fuze at the factory.

 

The relay is a hint that there's more going on here. I'd surmise that the relay enables the power feed to the 7-way trailer connector ONLY when the vehicle is in RUN mode (not in OFF or STARTING).

Can anyone confirm?

 

The 7 way is only hot with key in run position.