Troubleshooting a Liftmaster Garage Door
Look at both sensors, located near the floor on either side of the garage door. If both sensors are steadily lit, there is no obstruction. If one is flickering, it means the two sensors are misaligned or something is obstructing their path.
Coor Closes as It Is Reversing
Remove any leaves, dirt, debris or objects around or in the path of the sensors to see if that fixes the problem. Next try tightening up the wing nuts that fasten the sensors to the wall to bring the sensors back into realignment.
If either light is out, check the sensor wires attached to the white and black terminals on the overhead motor unit panel. Make sure they are properly connected and that a short is not occurring. If this does not solve the problem, consider calling a garage door specialist.
Motor Runs but the Door Doesn't
If you hear the motor running for at least 10 seconds and the door does not budge, a few things could be going wrong. The opener or the gears in the overhead case could be damaged or worn. Check for worn gears by removing the metal wrap-around cover on the overhead case. Any damage should be easy to detect with even an untrained eye.
Opener Light Continuously Blinks
If your opener has been working properly up until the light started flashing, but has been used several times in the last few minutes, the opener may have overheated and just needs to sit idle for a while to cool down. Next unplug the opener and leave unplugged for at least 20 seconds. If the light still flashes after replugging, your opener may have a problem, and you should consult a technician.
Door Lights Won't Turn On
Unplug the opener and open the face cover. Unscrew the light bulb and remove any corrosion you find at the base of the socket where there is a small metal tab. Screw in a new light bulb and replug the opener. This should solve your problem.