Troubleshooting Hydraulic Coupler Not Releasing Brakes When Trailer Is Backed

Updated 07/16/2015 | Published 07/15/2015

Products Featured in This Question

Dexter Zinc-Plated Brake Actuator - Drum - Multi-Fit Ball - Bolt On - 7,000 lbs

(180)

$375.29

Hook Probe Circuit Tester

(66)

$14.40

Question:

my 3 axle trailer with a Titan 20 hitch locks trailer brakes any time I try to back up. I replaced the lock out solenoid but still same problem. Also brakes line at reservoir seems to have pressure. I have to crack line open to release pressure so I can back up. any suggestions? thank you

asked by: Gene W

Helpful Expert Reply:

There are two prime suspects that would cause the problem you describe.

First, let's make sure pin on the trailer connector that's connected to the reverse light circuit is going hot when the tow vehicle is shifted into reverse. If you have a 4-way, it would be he center pin. If you have a 5-pole flat trailer connector, check the socket furthest away from the ground pin. For a 7-way, test the center pin. Use a circuit tester like part # PTW2993. The reverse lamp socket (or pin) should go hot when the transmission is shifted into reverse. If it doesn't, you'll need to find the wire that feeds the center pin on the 7-way or the socket furthest away from the ground pin on the 5 pole and tap it into the reverse lamp circuit on the vehicle.

When properly installed, the reverse lock out solenoid will shut a valve that prevents the brake fluid from flowing to the brake calipers when the trailer is backed. This solenoid will have two wires extending from it. One wire would ground to the trailer frame, the other would connect to the wire from the reverse light socket or pin on the trailer connector (it doesn't matter which is which).

expert reply by: Mike L