Trailer brakes engage in reverse?

[78bambam]

I was wondering if anyone has come across this problem. I hooked up my Ranger to my travel trailer for the first time yesterday, and everything seemed okay until I put it in reverse and started to back up. The trailer brakes engaged. I installed the Ford brake controller about a year ago but haven’t been able to tow the trailer until now. I compared wiring diagrams from the plug cover to the universal 7 pin and it looks to be spot on (except for being upside down). It doesn’t do this with our other truck (05 F250 diesel). Thanks in advance for any help.

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[BassRanger]

The Tow-Pro works in forward and reverse. Are you saying the brakes are engaging while braking in reverse, or they are engaging as soon as you shift into reverse.

 

[78bambam]

The brakes engage when you shift into reverse and start to step on the gas.

 

[BassRanger]

Likely, something is mis-wired or there is a short somewhere. Are the TBC and trailer brakes functioning correctly in forward. The unit glows red when it's applying brakes, so if your brakes are locking with it in the blue state, there's likely something other than the TBC sending voltage to the trailer brake line. I'd grab a multi-meter and start at the trucks 7 pin. First thing I'd check is your resistance between pin 2 and 7.

 

[BassRanger]

Actually, first thing I'd try is pulling the fuse for the trailer reverse light. Quick online search shows that it is 34 in the engine fuse box.

 

[78bambam]

It did just fine going forward. I didn’t notice what the brake controller light was doing in reverse, but it turns red going forward. I will try what you suggested when I get back from our trip. We will be using the big truck on this trip anyway. Thanks a bunch!

 

[canyonslicker]

almost sounds like the reverse lights are activating the brakes on the trailer

Bingo!! Or the cargo light wire is hooked to where the 3rd brake light is supposed to be wired. Turn on the cargo lights and try to drive forward. If brakes are on then turn off cargo lights to see if they release..

 

[Danager]

Possibly need to put the TBC into calibration mode again. Follow the process, then connect trailer at test again.

 

[D Fresh]

Bingo!! Or the cargo light wire is hooked to where the 3rd brake light is supposed to be wired. Turn on the cargo lights and try to drive forward. If brakes are on then turn off cargo lights to see if they release..

This seems very likely to me.

 

[Peragrin]

when was the last time the travel trailer was towed? I would more suspect a short in the trailer wiring than in the truck.

Edit:

do you know someone else who can back up and connect to it for a minute to find out?

 

[deleriumtremor]

when was the last time the travel trailer was towed? I would more suspect a short in the trailer wiring than in the truck.

Edit:

do you know someone else who can back up and connect to it for a minute to find out?

I thought the same thing until I went back and reread his OP. He said his other truck doesn't do it, so it sounds like the trailer is wired properly.

 

[78bambam]

Update: BassRanger hit it on the nose. Pulled the fuse for the trailer reverse lights (#34) and everything works as it should. Thanks to all for your input. By the way, this thing tows about 4000 pounds like a champ!

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