bigal1234

Along with the truck I got a bag with two parts in it. It was in the glove box but no indication of what they are for and exactly where to install them. I suspect one is a relay for trailer wiring and the other a fuse. Where do they go and why doesn't Ford include instructions?
Any help appreciated.
Al

srsfunk

After checking my owners manual on my 2010, I figured out that its for the charging circuit for the breakaway battery on your trailer. They go in the fuse box under the hood, or least thats were they went on mine.

MarksEB

They go in the fuse compartment under the hood. It's in the manual. I found it.

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Abn150

Correct, the relay goes in position #9 and the 20 amp fuse goes in position #21 in the power distribution box (fuse box) under the hood. They activate the constant power circuit (battery charging circuit) on the 7-pin trailer wiring connector.

If you have a rear view camera, there should have been a second bag in the glove box with a cap for the camera wiring harness, in case you remove the tailgate.

Bottom Dollah

Or someone else removes it while parked...........

Loaded4bare

Now I know why I need to lock my tailgate.....

mcfarmall

Will the constant power circuit charge an RV's deep cycle battery also? Does the deep cycle battery on an RV act as the electric brake backup in case of a breakaway?

My FIL has a 16 landscape trailer with electric brakes and a very small battery like one you might find on an electric start push mower mounted to the tongue to activate the brakes upon breakaway. I didn't know if the RV battery would act in the same capacity. It would be nice for the tow vehicle to charge the RV battery while travelling.

p38fln

For most RV's the constant aux power in the 7 way connector does charge the RV deep cycle battery, and for all trailers with electric brakes, it charges the breakaway battery.

For all enclosed trailers with interior lights, this is also the circuit that lets you turn the interior lights and exhaust fans on.

Ford doesn't install the fuse and relay for you because the powered up +12V circuits seem to corrode and some people buy a Max Tow truck and dont pull a single trailer its whole life.

mister_d

I've been told that your tow vehicle will only trickle charge your camper battery... one amp at best. You will be unable to charge the battery if less than a continuous 72 hour drive. I've noticed that the tow vehicle will keep the battery as is and replaces the draw from the co2 detector and any other parasitic draw.

bigal1234

Thanks for the replies. And in a travel trailer or fifth wheel the deep cycle batteries do power the breakaway switch.
Al