garage door stuck at open position
Yesterday, I opened the garage door with my remote and the door went up fine. However, when I tried the remote again, the door wouldn't come down. remote, wall switch nothing worked. So I disengaged the arm that connects the door to the carriage and manually pulled the door down.
The door comes and goes up easily with little force. So I am guessing that the springs are fine. (Uses torsion springs).
Today I took a closer look at the overhead opener unit. When I pressed the remote the carriage was further pulled back (looks like the motor keeps opening the door) and stopped when it was being pushed into the opener unit. (without the door connected to it, it pulled back all the way it can). It seems that the motor only tries to pull up the door and does not move in the other direction. I tried to move the limit switch with the screw-driver, and start the motor with remote, and still the motor tries to move the chains in the direction of pulling up the door. So how do I make the motor reverse directions?
The model I have is Allister All-O-Matic model AR-7D. (very old, I am not sure how old) I have the manual.
Any help will be appreciated.