Lift master 91LM

If the remotes will operate the auto door lift, then the probable cause is either the switch on the manual panel is bad or the connection to that panel isn't hooked up properly to the main control board. I'd claim on the warranty and/or get the original installer back in to look at it as opening it will more than likely void any claim you may have against it for a manufacturing defect.

I tried the
DIY service and repair manuals from a website and it actually helped me repair transmission problem in my jcb 3cx site-master. it wont move forward or reverse, engine is good both solenoids for forward and reverse work.
I don't have much technical knowledge but I just followed it step-wise, and works perfect! got it from www.reliable-store.com

It seems that the reciever part is defective, likely to surge or lighting, you have to have that module replaced.
Tony

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/tony_a41fa0b801734e2f

Check where the wiring harness goes into the drivers door from the hinges. There is a cover over it undo the screws and check for broken or almost broken wires. these are the wires for the master switch, if they get brittle those things wont work.

Please do not attempt to set the tension your self. Call a garage door service Co. Broken arms and fingers result. It is not worth the attempt. Those tension spring do all the lifting of the door and have to much torque to mess with.

Don't know what malfunction means.

OK, ONE DVD MUST be set as MASTER and ONE as SLAVE. The master MUST be on the "End" of the cable, the SLAVE, on the other. First try with ONE drive, and if you get it working, swap them out too at first, then after establishing that it works OK with just One, the MASTER, then introduce the SLAVE. Do Not forget to RE-JUMPER between swap outs.

You may need a C943 as the + can make the siginal different.[Chambelain or Merlin]

u have a defective electric window motor so no override will work, u must take the door apart and replace the defective electric windowe lift motor.