Brakes locking while backing!

[1badz71]

Recently had an issue with brakes locking while trying to back trailer. Used the "key" in the tongue and got it in the garage. Where do I start diagnosis. I have towed for 15 years and never experienced this issue.

[Tim619]

Reverse lights coming on? My old '02 Dodge Ram with a manual transmission had a microswitch on the side of the transmission housing that was activated when I threw the old girl into reverse.

Bet there's a switch on an auto too.

First thing to do though is check the fuse for the reverse lights.

[joefish]

Had same issue recently. After checking fuses and obvious things I discovered the ground on my trailer was rusted and corroded. Removed ground wire cleaned up the connection reinstalled tightened the bolt and all was good.

[mactlman]

should hear a click in the tongue when put into reverse IF the trucks reverse lights are working and wiring is good to the trailer

[wmitch2]

1st. Check for Back-Up lights are coming on. No lights means no power to the lock out solenoid. Check the power at the plug on the truck, then check the trailer plug.

2nd. Check the ground wire on the trailer. Make sure the wire to the trailer plug is connected to the trailer frame. Clean all rust and use a new screw or bolt however it makes the connection.

ALSO, check the fuse on the truck located in the engine compartment usually at the front of the motor. Your owners manual will tell you which ones are for the trailer.

[Flash2]

Had this happen to me after using another truck to tow with. Looked at everything ended up being the plug prongs. I bent them back out and been ok ever since.

[DewRonInc]

The lockout sol is probably shot

[billnorman1]

Check for 12 volts on the purple or blue wire on the trailer with the truck ignition on and in reverse. Check it with the plug connected. Use the trailer frame for ground.

[krindgen]

My money's on the ground or a bent plug tab if it's a round plug. I've been fooled several times on a bad solenoid and truth is, they go bad very rarely.

[Chasman]

Check back up lights on trailer to see if they come on. The second thing is to look for is a short. Start by looking where the wires come out of the trailer frame. This was the location I’ve found wires bare due to wires moving / rubbing while towing. Of course if you have any of these, you probably have a blown fuse.

[1badz71]

Thanks for all the replies, been too cold here to look at the trailer. Truck backup lights are good, will be cleaning plug and ground tomorrow, have a feeling the answer will be corrosion!

[Team Mud]

How old is the trailer? Disk or drum brakes ?

The older Drum brake trailers didn't have a reverse lock-out solenoid

[bcreek]

The center(1/4" diameter) pin on round plugs screws on and off. Mine came unscrewed and was lost therefore no reverse solenoid action. Something to check.

[htbboats]

Depending on your truck…. I had a “16” GMC that I had the same trouble. It has a module that the wire that activates the backup solenoid goes thru. The back up lights worked but I was not getting current out of this module to operate the solenoid, thus the module was bad. I never found out the purpose of the module. I bypassed it by running the “solenoid wire” directly to the back up light wire and all worked fine.
Something else to check.

[donniec]

I had the same problem with the module on my high country, Chevrolet dealership charged me to the tune of $740 to diagnose and replace. I screwed mine up by using a ramp that I had to back way out into the water to get the boat off the trailer. Dealership service technician said if it gets submerged it will get it every time.

[BMCD]

My experience is the plug is a point of failure here. 7 pin round very common for male ends on the truck side to get pushed in and do not make contact.