I have a 2023 F450 with 5000 miles. I frequently tow and the 12 volt that goes to the trailer battery through the 7-way plug stopped working. I replaced fuse 76 under the hood it still does not work. Does anyone have suggestions for what I could try next before I have to take it to the dealer?

 

Maybe a really simple question, but how do you know it's not working? Try this (just humor me), leave the truck in drive with the parking brake engaged and then measure the 12V power at the 7-way switch.

 

I will measure the voltage tomorrow at the plug. I work for a rv rental company so I was able to try it on 3 different trailers. I also tried the plug in the bed and at the bumper and neither worked.

 

It could be a failed relay.

The 2017+ Super Duty trucks are strange in what it takes to activate the charge current at the 7-pin. On my truck, I have to start the engine and then press the brake pedal. Others have said they must have the driver door closed. It's odd how different trucks require such different methods.

 

Check out this youtube

 

Make sure to tap on the brake before checking.

 

I saw that video not long after it first came out. Probably one of the most thorough troubleshooting videos on this topic. It also prompted me to buy a test light like he had.

 

I noticed on my 2020 that to get power at the plug I had to tap the brakes and squeeze the brake controller to get power to the trailer but on my 2023 it worked as soon as I plugged the trailer in without stepping on the brake, closing door, etc. Ford changed something with the logic in the 2023 models

 

Or there's a Ford programmer with a sense of humor making trucks behave randomly.

 

so please keep these things in mind.
The doors all have to be closed with the engine running, truck brakes applied once, AND it has to since that a trailer is connected. so some type of load on the connector hot wire or a load on the trailer light circuit.
IF you have push button start you must also have the keys in the cab when checking for power.
So, doors closed, engine running, load on the trailer plug, and key in the cab truck brakes applied at least once after trailer is connected.
If you have the factory trailer brake controller there is no other power fuses.
I hooked up a volt meter to my trailer output so I can see what turns it on and off, and I also have a Bluetooth meter on the trailer battery so I can see when it has power from the truck.
Untill I knew all this it was a pain to trouble shoot

 

WHY FORD WHY. whats wrong with just having it supply power soon as ignition is on? i've replaced so many fuses on the dump trailer due to this lol.

 

Not just Ford. Vehicle electrical systems are complex computer-controlled systems now.

 

Just to add..... I've had 2017.2019, 2020 F-350s towing our 2017 5th wheel with Electric over Hydraulic brakes, using the Ford OEM brake controller without any issues. With my 2022 F-450 I was getting intermittent Trailer Disconnected messages when towing and immediate trailer disconnected message any time I pinched the manual trailer brake paddles. I called the dealer who supplied the brake kit and he said that some recent Ford brake controller owners have reported the same thing. He recommended that I install a Brakerite Adapter module for EOH that Intercepts the verification signal to prevent false error codes. https://www.etrailer.com/Accessories...er/DX35FR.html and install it. It immediately fixed the fault.

 

Another thing. I installed an simple yet inexpensive Bluetooth voltage monitor on my RV Battery It allows me to monitor the trailer battery voltage with my phone app anytime, plugged in or when towing. Low and behold, unbeknownst to me, when towing my battery voltage was dropping to below 11 volts. After troubleshooting I found out the the disc brake installer miswired my installation and I was not getting the truck's 7 pin charge voltage to the battery. I fixed the wiring error and now I maintain at least 13.6 volts at the RV Battery when towing at all times.

 

Not to revive a old thread but I was trying to google and find out why my 2023 f350 keeps blowing the fuse on my 2024 dump trailer. It isn't all the time, so far when i notice it blown of course is after the trailer battery is low. Yesterday the battery was dead and fuse was good. I got the bed lowered and the fuse was still good. By the time i got it home to plug it in was when i noticed the fuse was blown finally. It is the 20 amp fuse by the traieler battery that keeps blowing.. Did you figure out a solution or just keep a box of fuses on you? Or by chance know what fuse it is on the truck so I can make sure to match the truck and trailer to the same size of fuse? My owners manual doesn't have any spot for trailer charging.. thank you.