2021 F-150 trailer brake issues

[Neighbor]

This may be addressed in detail on another thread, but I couldn't find it. I recently traded for a 2021 F-150 max tow lariat to tow my 2018 Mesa Ridge 2910RL travel trailer. There was a recall on the tow braking system and I had that taken care of prior to a trip to Colorado. Long story short, I had intermittent "Trailer wiring fault" and "no tailer attached" warnings many times while in the mountains and sometimes I had trailer brakes and sometimes not.
I checked trailer wiring, connections, redid grounding wires on trailer, cleaned wiring plug multiple times, but in the end nothing seemed to last long but we made it home safely. Took it back to my local FORD dealer that handled the recall this week and after parts of 2 days (2nd day with trailer) checking, they swear it's not in the truck, but the trailer. This same trailer worked fine on the 2010 F150 that I pulled it with previously.
I've read online solutions that range from changing the plug connector, adding a resister inline so truck "sees" the trailer better, changing from LED lights on trailer to incandescent, etc.
Anyone have this problem and have a "for sure" solution?

 

[sandyhillbill]

Maybe find a friend that has a suitable truck to tow it and see if the problem
stays with the trailer or this might prove that the problem is with your new truck.

The dealership should have done this for you.

 

[BCM-ORO]

Try the adapter. Do you have hydraulic brakes on the trailer? If so you may need the brake module for it. I had the problem with my 22 F350 and the recall and TSB took care of it.

Here’s the adapter if you need it.

https://www.amazon.com/gp/product/B00AF ... UTF8&psc=1

I’d also suggest checking out the truck groups on Facebook… 150, Super Duty, etc. Lots of information about all of that on there.

 

[Rigdon]

My 2021 f350 had a similar event, it was a brake magnet in the trailer rubbing sometimes. The wires shorted out occasionally not all the time.

 

[Neighbor]

Since the original post, I've taken the trailer to an RV repair shop and they couldn't find anything wrong with brakes on trailer. Since then I hadn't had any problems until this past weekend on a trip to Beavers Bend. On the way we drove in rain and about 70 miles later, I got the "trailer wiring fault" message and had intermittent brakes for about 10 miles then everything seemed OK. On the way home 4 days later it was problems all the way - sometimes had trailer brakes and sometimes not. BTW: I do not have hydraulic brakes on the trailer.
I understand the problem is difficult to troubleshoot because apparently it's so intermittent - sometimes 100 miles after hooking up before a problem shows up - but from what I read on various truck forums this is not just a problem I'm having, but I don't find anyone that's found a "for sure" cure. Frustrating and dangerous

 

[JKJavelin]

Twice in the past couple weeks I've read/heard of intermittent brake problems caused by wires rubbing while passing through the axle. Here's a recent video by Ray repairing it.
https://youtu.be/neBPGpq55y8?si=bxq9Vnex9I7yzvnc

Hope this helps.
JK

 

[Neighbor]

Thanks for video! I'd already decided that I needed to check out "in axle" wires and possibly the one coming down the side frame from the front. This backs that up. I'll advise what I find.

 

[Neighbor]

I think I found the problem. When I pulled the brake wire that was run through the front trailer axle, I found 2 or 3 rubbed spots where the insulation was very thin although it didn't look like the copper wire was actually exposed. However, when I pulled the original wire out of the rear axle, there was a 1 to 1 1/2" spot where the copper wire was actually exposed. I pulled new (slightly larger) wire in both axles and have it all reconnected but haven't hooked up and done a test run yet - not that the test run will prove anything because sometimes this intermittent problem didn't appear for 100 miles or more. I do feel like this was the problem, however.

An item of interest was that there was moisture inside the axle because the wire was wet when I pulled it out. The last trip when I had a lot of trouble with the "trailer brake fault" issue coming home, I had driven nearly 2 hours in the rain right before I set up camp 3 days before. I'm sure the moisture aggravated the issue. As far as I know, the only water access would be through one of the 1/2" holes at each end of the axle where the wire entered and exited - there are rubber gromets, but certainly not water tight. I'm considering whether it would be beneficial to seal with silicone but haven't yet.

Thanks JK