Troubleshooting Demco Reverse LockOut Solenoid Not Clicking When Activated

Updated 03/25/2026 | Published 03/22/2026

Question:

Hello, I bought the master cylinder for my boat trailer. Ive had it on for about a year or so now when I reverse the boat, it works intermittently. I have already tested my 7 wire plug. I knew Im getting correct voltage. However, I do not know if the solenoid is working correctly or not. I dont hear a click when 12 V is applied now. I am thinking either the solenoid is bad. Or does the push rod assembly go bad to prevent the trailer from reversing? As in maybe something is not online, correct.

asked by: Hoss F

Expert Reply:

Hey Hoss, you should definitely hear the solenoid of the Demco Replacement Large Bore Aluminum Master Cylinder w/ Bypass Solenoid # DM6113 clicking when it's activated so something is going on. I would suspect the wiring to the solenoid first though so I would try checking to make sure the reverse light circuit is making a solid connection to it and also that the ground wire is also making a solid connection. Worth mentioning is that either wire can be used as the power or ground as the solenoid is not polarity sensitive.

You can also try running a jumper wire from a vehicle battery to the solenoid to see if you can hear it click too. Try that and let me know what you find.

expert reply by: Jameson C

Hoss F.

3/23/2026

Yes the reverse traier light is working verified. 12v. However the solenoid will not click. But I did find out the coupler actuator shock is shot. I think when in reverse. The couple is sticking and cause my brakes to activate vs the shock stay unloaded when reversing.

Jameson C.

3/23/2026

@HossF Interesting. Well if the shock is bad it's a good time to replace it either way.

Jack

3/24/2026

MAN MINE LASTED ONE SEASON, AFTER PULLING IT OUT FOR THE NEXT IT WAS STUCK SHUT, SO I PULLED THE THING APART AND INSALLED A NEW REVERSE SOLENOID AND WORDED GREAT THE REST OF LAST YEAR. PARKED IT FOR 4 MONTHS AND IT IS STUCK SHUT AGAIN. I JUST BOUGHT A DIFFERENT BRAND SOLONOID AND EXTRA FOOT OF BRAKE HOSE TO MOVE IT OUT TO THE SWING TRAILER OPENING SO I CAN EASILY REPLACE THEM IF THIS ONE IS NO BETTER. BUT AT THIS POINT THE MASTER CYLINDERS ARE FINE, THE REVERSE SOLONOIDS ARE JUNK.........

Jameson C.

3/24/2026

@Jack what solenoid did you replace it with this last time?

Jack

3/24/2026

I THINK IT WAS A DEXTER ONE, I WOULD HAVE TO CHECK WHEN I GET OFF WORK. IT HAS A BLACK TOP AND ONLY ONE WIRE SO I WILL HAVE TO USE ONE OF THE 2 THREADED MOUNT HOLES FOR THE GROUND OR MOUNT IT.

Jameson C.

3/24/2026

@Jack Let us know if you get a chance.