Just had my rig in for battery service at RV dealership. Veteran service tech came out to discuss no power from truck to trailer - walked to cab and held brake down for 7 seconds and boom instant power to trailer through 7way. Apparently it is “off” by default and you activate it by plugging into the 7way and pressing brake pedal for 7 seconds.

 

Thank you, that was the answer I was looking for.

 

Here you go! Ford Special Service Message:
SSM 46257

"All 2017 F-Super Duty vehicles equipped with a factory trailer brake controller (TBC) utilize a trailer module (TRM) which initiates the trailer charging system. For trailer charging to operate, the TRM must detect a trailer is connected and a brake pedal input before charging will be present at the trailer connector. Adding the trailer battery charge relay and fuse into the battery junction box are not required to operate trailer charging with a TRM."

 

You can't add the relay anyway. There are no metal prongs to stick it into. The fuse does go in.

 

I got a quick charge in the morning with a battery booster. I don't use the brakes much anyways. I drive tractor trailer and mostly use the engine brake and stay off people's asses. More reaction time that way.

 

My 2019 F250 won't charge until it is above an idle. This won't explain why you didn't charge while driving but when testing at idle it will fool you. My snowmobile trailer interior lights where hooked up to the battery feed wire. This made the interior lights always hot on my other trucks, even when the truck was not running. But on my ford the lights didn't work when we where loading the sleds in the dark with the truck running. I later figured out they were on all the time I was driving. LOL. Ford went to the trailer module to control trailer lights and power. It's not a bad thing you just need to know how the module controls things. I called 3 different dealers before I found one that told me what the module on my year truck did with the battery power. It seems these modules change function slightly from year to year. If your in Maine much the Bangor dealer is where I got the correct information for my year truck.

 

I live in Maine. My son-in-law is the service manager at Hight Ford in Skowhegan. This was my first long tow. From Maine to Florida. Ford should have put some of this info in their owners manual. I have a 2017 F350 dually diesel and it was made for towing and you would have thought Ford would have thought of this. I did add a 30 amp M series fuse in position #27. I have a Curt 7 way plug coming tomorrow that have 3 diodes in it to fool the tow computer, then you do not have to the trailer set up. Just hold the brake pedal for 7 seconds. But why did they do this. I drive tractor trailer in Maine and my Peterbilt is nothing like this.

 

You are absolutely correct, when a manufacturer makes a change that will impact something as important as towing (like with a F250 or up series) they should at least put the new info in the manual. Hang a tag on the electric brake lever like: this works different than before or to make this work you FIRST have to do ?? It's not like they don't put enough unless warning stickers on them already. We already know the exhaust can burn you, they could trade that warning sticker for a trailer brake note. I'm not very far from Hight, they are good guys over there they have done some work for me before.

 

This happened with one of my dads trucks had this issue, the fuse was never put in .

 

Some people and Ford say you do not need it if you have the factory brake controller. I did put it into mine and followed the procedures that people have told me to use. Do the trailer set-up then hold the brake down for 7 seconds. It worked for me yesterday here in the campgrounds I need to keep the batteries charged up and that did not happed on the way down from Maine. It sucked.

 

After thinking a little about this tread, having to apply the brake pedal makes sense. If you're at a campground and the trailer is connected to the truck you wouldn't want the trailer to drain the truck batterie(s).
Just my opinion. BTW my truck charges just fine.

 

The problem is that your DRV has the turn signals separated from the brake lights. Somehow, the truck reads that the trailer is connected by sensing the turn signals when the brakes are activated. I solved this by wiring a couple spare LED market lights before the module separates the brake and turn signals ( located in the battery compartment)

Also, my tuck does not charge while in park. When testing, I put the truck in neutral and apply the parking brake.

 

I have a 2017 F450 and it charges the DRV batteries. The info about the trailer module is in my manual and I had a time understanding why the truck would not charge the trailer like the earlier 12 gmc did until I found it in the manual. The DRV I have is a 2014 with 3 disc brake axles and all works ok with no work arounds but have heard of a few others that had issues. I had an inverter generator, Honda, and it would not charge using the trailer plug. Talked with honda and had to add a 115 volt plug with a jumper wire between grd and neutral to indicate a ground, then it worked fine. Check with the gen manufacture maybe the same problem. Hope this forum has helped you.

 

You are right, I misread your post.

 

I may have found a fix for this. My Curt 57003 adapter will be here tomorrow. It has 3 diodes in it to fix the charging problems. Take the bed 7 way plug and exchange this Curt one in it's place. Plug and play I have heard. Will let you guys know. FORD you suck sometimes!