Hi All,

I'm having an issue with my truck and trailer and I'm hoping for some insight.

2024 F350 CCLB Limited and 2022 Alliance 32RLS fifth wheel trailer. The trailer worked flawlessly on my last truck(2019 F250 CCLB Limited) and since we got the new truck in February we have and the same issue every single tow. I don't have pictures of the warning banners that appear on the cluster but I get two, #1 trailer light fault, #2 trailer break fault. When I get the faults it is always 1 hour and 10 minutes into the tow as long as the truck hasn't been shut down. Shutting down resets the faults. If I don't reset the faults I lose the right turn signal. I don't know if the brakes are working, they do manually. I have had the dealer diagnose the truck and they find nothing amiss, but they don't run it for the 1:10 it take to produce the faults. I have been through the trailer as well and even changed the pigtail to a pinch connection 7 way that was recommended on the forum for trailer connection issues. I have one more thing to have checked on the trailer at the factory next month, something about the brakes being wired incorrectly but it's not likely.

If I didn't lose my right signal I wouldn't be worried about it, annoyed but not concerned. It's a real safety issue with a 35' trailer.

The 1:10 minute time to fault seems really odd to me but we had a tow last month of over 3 hours and it happed twice going and once coming (we stopped and shut the truck down and that seems to reset the time).

Has anyone else run across this type of issue? I don't see the dealer being able to fix it as they can't get it to show up.

 

The specific TIME into a tow seems to indicate it's an issue with the truck, possibly a module that somehow gets confused at that point. It doesn't scream that it is the trailer, because a bad ground would usually show up over bumps or any motion of the trailer. I suppose you could try running dedicated ground wires for the light you're losing - I need to do that with my flatbed, just this past week I had to undo the ground for the passenger turn signal, re-grind the contact point, clean everything, and put it back together to get good ground again. That's the problem with relying on the trailer frame for ground, if it's exposed to water/salt it will eventually rust up and you'll lose your grounds (not that wires can't be damaged or lose ground either but there's at least some protection there).

 

easy thing first
i know you checked...however
the TBC system in our trucks is VERY VERY sensitive to loss of ground from trailer to truck VIA the umbilical cable
check and make sure your trailers harness is grounded and not corroded

then clean the connector and truck end
2nd check the breakaway battery connection and its wiring, if its the house batteries that run the emergency braking if trailer departs, make sure the wires are connected and not corroded or broken
if it has a small battery in a box somewhere to apply emergency braking, then check it for charge or if its serviceable
my car hauler trailer has a small battery for emergency brake away and it looses charge and will give a quick notification and then it gets charged by the truck

if lights and brakes work until you drive for a bit.....
8 to 10 its a ground or umbilical issue

 

We had it at the factory last month and they checked the umbilical, it's a standard practice they do with all coaches that work on. I had just replaced the umbilical before the trip. it did it before and after. I'll double check the house batteries connection. I'm not sure where the breakaway get it's power but I'll trace that back.

 

Pretty sure there is a TSB out from Ford for that issue. I’d take it to your dealer.

 

does anyone have the TSB number if there is one? I had to walk in the TSB for the passenger side lockout hub to the dealer. They couldn’t find it.

 

I had the same problem with my 2025 450 Platinum, had no problems with my 2020,in and out of the dealers,i end up installing a Curt Led Electrical Adapter from E Trailer, looks like a pigtail , it connects into truck then to light cord. It has built in resistors for computers that don't or have a hard time recognizing Led lights and circuits ,plugged it it in and problem solved. Went from Ma to Fla and back without a hitch.Was constantly getting messages lights out, trailer disconnected, brakes not working (electric over hydraulic) brakes, cured it all.

 

One other thing not mentioned, check the harness to the socket in the bed. Pull it out of the sidewall, disconnect it, check it for corrosion, put some dielectric grease on it and reconnect it, then do the same for the harness above the spare tires, and the socket in the bumper. Corrosion in any one of these locations can affect connectivity between truck and trailer. I would especially inspect the one above the spare as that one has been known to cause issues.

 

I’ll give this a try, already ordered one.

 

I did all that reassembled with dielectric grease truck was brand new, figured maybe one of the connecters wasn't plugged in properly from the assy line, even put a dedicated ground from the fifth wheel to the pin box.I start looking into RV forums and found out a lot of people with euro suvs (MB'S and BMW'S were having trouble with lights and brake functions pulling small Airstreams and went to the Curt adapter and solved the problem so I figured I'd give it a try, Problem solved, later I heard about a TSB.I never went back to the dealer, most of those so called techs don't know their *** from a hole in the ground.