2019 F250 will not charge trailer battery

[Steve & Sheryl]

. . . the 2019 you MUST HAVE THE DOORS CLOSED and step on the brake pedal for a few seconds to activate the controller. If you try it with the door open it will not activate.

I've sorted this out today in the driveway for my 2020. It did have fuse installed. I just needed to follow Jerryr's advice.

You can see the difference on the Victron, I don't know how to check this otherwise. The stepping on the brake pedal part was the trick. I needed to press the pedal hard, sometimes twice, to activate the circuit. After that it stays live until I shut the truck off, even after opening and closing the doors. Last time, when the DW checked the Victron while we were moving, I had been very light on the brakes. I suspect the circuit doesn't fire up until you brake hard enough to activate the controller.

I'm just adding "pump the brakes a couple of times" to my mental drive-off checklist. That will get a little juice flowing.

Thanks everybody for the discussion!

[Jims94vmx]

Just for giggles, try turning on lights to activate charging....pretty sure at my last harvest host that activated mine. 2017 Ford

[TheLexx]

So have we reached a consensus. Is fuse 27 actually required or not?

[Jerryr]

So have we reached a consensus. Is fuse 27 actually required or not?

Not on your 2017 or newer models but yes on 2016s and below. If you look at position 27 on your 2917 I suspect you will see there aren’t even any pins in the truck side.

[TheLexx]

Not on your 2017 or newer models but yes on 2016s and below. If you look at position 27 on your 2917 I suspect you will see there aren’t even any pins in the truck side.

Thank you. That's what I thought.

[Jeb Ogburn]

I found on our 2019 f350 with towing package and all, that is wasn’t charging the Rv batteries. Since I’m using a Reese Goosebox ball hitch with Ford factory ball, I programmed the trailer as a “gooseneck” trailer. Not until I changed program setting from gooseneck to Fifth-wheel, then truck started charging Rv batteries. The fuse slots that others are mentioning, were not needed. So I’m going with the “close driver door, step on brake, and put tranny in Drive”. I also put a volt meter w/switch on my hitch box so I see what the voltage was doing going down the road. I can turn the volt meter when parked or not needed.
It’s a great quick visual Voltage indicator.

[mando1966]

I was dealing with the same issue then learned it wasn’t an issue at all. Same scenario. I tested for power and when there wasn’t any detected at the plug, I checked the fuse box. According to the owner’s manual, there should be a relay and a fuse. Mine was relay In slot # 37 and fuse in #27. To my surprise, both were missing from the fuse box. I went and did a little digging and found out Ford had put out a memo regarding this confusion. From Ford:

SSM 46212:

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. If testing of the trailer charging system is required without a trailer, refer to the updated diagnostics and system operation found in the online Workshop Manual (WSM), Section 417-01 Exterior Lighting.

[Steve & Sheryl]

Just for giggles, try turning on lights to activate charging....pretty sure at my last harvest host that activated mine. 2017 Ford

Tried turning of the lights. It didn't activate the circuit in the F250. Looks like pumping the brakes is it.

[Roll With The Changes]

Time to revive this thread...

I bought a new cargo trailer and the interior lights wouldn't work. I didn't think much of it; it's a simple system so it should be easy to fix right? Well... I initially found the culprit which was a protection diode to prevent the brake battery from powering the interior lights... No problem, just plug in the truck and the lights should work.... nothing. Measure voltage at the truck connector... no voltage... check the fuse... good... scratch head... is the truck broken?... ask google.... it brought me back here!

I followed the guidance here and it turns out there is nothing wrong... except the system design. This is almost impossible to diagnose without external guidance and help. If you follow the procedure (door closed and brake on to activate the system) then get out to check voltage, the system is deactivated again... impossible to check by yourself.

I have two questions here: Why did Ford make this so complex and also @Jerryr why do you know so much about how Ford set this up? This is so non intuitive.

Thanks to all for this thread. It solved my issue in a couple hours instead of weeks of troubleshooting!

[Heavy Half Ton]

Time to revive this thread...

I bought a new cargo trailer and the interior lights wouldn't work. I didn't think much of it; it's a simple system so it should be easy to fix right? Well... I initially found the culprit which was a protection diode to prevent the brake battery from powering the interior lights... No problem, just plug in the truck and the lights should work.... nothing. Measure voltage at the truck connector... no voltage... check the fuse... good... scratch head... is the truck broken?... ask google.... it brought me back here!

I followed the guidance here and it turns out there is nothing wrong... except the system design. This is almost impossible to diagnose without external guidance and help. If you follow the procedure (door closed and brake on to activate the system) then get out to check voltage, the system is deactivated again... impossible to check by yourself.

I have two questions here: Why did Ford make this so complex and also @Jerryr why do you know so much about how Ford set this up? This is so non intuitive.

Thanks to all for this thread. It solved my issue in a couple hours instead of weeks of troubleshooting!

The beauty of a dc to dc charger cannot be overstated. With the victron unit we have, it is bluetooth also, so you can watch the 38 amps going into the battery when you are going down the highway. We also can bluetooth to the bmv712, and see the state of charge of all those lithium atoms.