What Would Cause Electric Trailer Brakes To Lock Up When Vehicle Is In Reverse?

Updated 04/22/2025 | Published 03/28/2025

Question:

I have a Wells Cargo Tote Wagon, with electric brakes. Just came back from a 2,000 mile trip, and was backing into the driveway, when the rear wheels locked up. I could free them up by pulling forward, but they kept locking up after about ten feet of going backwards. I unplugged the connector, so no power was getting to the trailer, but the brakes still lock up, but only going backwards.

asked by: Lee W

Expert Reply:

Hello Lee, thanks for reaching out. If your have a trailer with electric brakes and they are locking up when you back up, this is most likely because you have a short between the reverse light circuit and the brake output circuit which is locking the brakes up.

Trace the two wires for these circuits and see if you can find where they might be shorting out together. Look for any damaged or frayed wire. Or it could be cause my corrosion on the connectors. Repairing or replacing the wire as needed should resolve the issue.

I hope this helps. Leave a reply below with any other questions or comments and I am happy to continue to assist.

expert reply by: Jesse M

Lee W.

4/22/2025

Hi Jesse, Thanks for the response. I will investigate whether there are some shorts or frayed wires. It's an old trailer, and I had to rewire the brakes last year, so I may have done something wrong. It does seem to be strange that only the rearmost wheels locked up, and the ones in front did not. Also, why would they lock up if the connector was disconnected? I'll let you know if I find anything!

Jesse M.

4/22/2025

@LeeW Yes it still sounds like a short is the most likely explanation. Hopefully nothing got fried. If the brakes are fairly new, it might be easier to just re wire the trailer with a whole new harness. That should take care of it.