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We bought a new travel trailer a couple of weeks ago and took it directly from the dealer to a campground, about 90 miles. The brakes on the trailer worked normally. Hooked up last Saturday to come home and no brakes. When I would apply the brakes on the controller it would tell me trailer disconnected but everything else worked, lights, brake lights and turn signals. I had to drive home 225 miles with no trailer brakes. Fortunately it is 4 lane all the way, except for the last mile. I slowed down and kept my distance from the traffic ahead of me.
I did some investigating today. At first I thought it was a truck issue but I hooked our F150 to the trailer and got the same message. I checked all the connections under the trailer and saw nothing unusual. I did a check at a junction box under the trailer where the 7 pin cord is connected to the wires feeding everything, including the brakes. Even though the truck is showing trailer disconnected I did get a reading when applying the brakes with the controller but it was only 11.2 volts. Not sure why it's so low. I know it's a long shot but thought I would ask if anyone else has run into this. I have a trouble ticket started with Grand Design and will try to get them to cover a mobile tech if I can't figure out the problem.
Last edited by FishRanger; Nov 17, 2025 at 07:04 PM.
Since it happens with multiple trucks, it's definitely a trailer issue.
Could be just a poor ground at the brakes. Could be the plug on the trailer - not sure which kind you have but some are superior to others. I've had good luck with the 'spring style' plugs instead of the molded-in blade style, I've converted every trailer I own to that. The trailers we have for work, our maintenance guys keep buying the cheap plugs because 'We keep getting trailer disconnected messages' and it NEVER solves the problem. ONE trailer works flawlessly, because we took it to an actual repair shop and they put a GOOD plug on it.
Since it's brand new, I would say let Grand Design take care of it under warranty.
Ford brake controllers have issues when it comes to trailers where the electric brakes are low resistance. They use load sensing to tell if the trailer is connected and enable trailer brakes. Had this issue with multiple brand new trailers, usually ones with single axle brakes. I added an led resistor to the brake single wire to ground which increased the brake signal resistance and the trailers all started working. Been a Ford issue for like 10 years now with their built in brake controllers and they still refuse to fix it.
Note, the color never match the traditional colors but the box is marked completely..
This is EXACTLY (well different brand but same concept) what I put on my flatbed, solved 99% of my issues. The 'spring' style connector makes a better connection to the plug on the truck.
Rear lights are still grounded through the frame though, and I've had to re-grind and reattach the grounds. Usually always happens when I'm in a hurry, then I don't have time to mess with it after the fact, but I need to just run dedicated grounds for the lights. Looks like the brakes already have a dedicated ground so I'm good there.
Make sure the trailer brake or magnet wiring within the drum hasn't or doesn't have a spot in the wiring where it touches ground, as in a wire that has been rubbed enough to lose it's insulation and now grounds out the positive side from the brake controller. Fought this on my gooseneck after installing new backing plates and drums, checked and checked my wiring, it wasn't until I isolated my DS rear drum that I found the culprit, the factory installed brake wire retainer clip pinched the wire enough to cause the issue. Brake controller just flashed when brakes applied....sometimes and at the worst possible time. None of the trailer brakes worked when this occurs. Good luck and hope this helps.
My son has a truck with a Prodigy, I think, controller. He hooked up to our trailer and again, no brakes. Lights are fine. I have traced everything I can and checked all connections. Nothing that I can see. It's under warranty so I'll let the dealer handle it from here. Grand Design added anti-lock brakes and sway control to this year's models which may make it more complicated but maybe not.
A common point of electric brake failure is the wire that runs from left brake to right brake. Most of them run through the hollow axle tubes. Especially if the trailer has some miles on it, but often even if it doesn't, the wires chafe on the rough inside of the tube, or on sharp edges on the holes where the wires enter/exit. You'll never find that unless you pull that wire out of the axle, and at that point, don't put it back. String it along the outside of the axle tubes.
A common point of electric brake failure is the wire that runs from left brake to right brake. Most of them run through the hollow axle tubes. Especially if the trailer has some miles on it, but often even if it doesn't, the wires chafe on the rough inside of the tube, or on sharp edges on the holes where the wires enter/exit. You'll never find that unless you pull that wire out of the axle, and at that point, don't put it back. String it along the outside of the axle tubes.
Sounds like this was a manufacturing defect - they bought the trailer and took it directly to a campground, and discovered the issue when trying to pull it home.
That said, it could ALSO be a rodent issue, but you would likely see chewed wires if that were the case.
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