Why does my garage door reverse as it is closing?
All garage door openers manufactured after January 1, 1993 include the federally mandated Safety Sensor Reversing System®. These sensors are found 4 to 6 inches above the garage floor and protect the door opening with an invisible beam. If there is any problem with the safety sensors, the light bulb on the opener will flash 10 times and the garage door will not close unless constant pressure is applied to the wall button.
Both the sending and receiving sensors have a small LED light to help us align and troubleshoot them. The LED on the sending eye will glow regardless of alignment or obstruction. The LED on the receiving eye will go out when the beam is obstructed, and it will flicker if out of alignment.
The first step is to make sure that each sensor has a steady glowing LED light. If both lights are on, but one appears to be flickering very slightly, chances are the sensors are misaligned. To check for misalignment, first obstruct the beam of the sensors so that they cannot see each other. When the beam is blocked, the indicator light on one of the two sensors will temporarily go out. This is the receiving eye. Remove the obstruction so the light on the receiving eye comes back on. Then loosen the wingnut on the back of this sensor. Move the sensor around and make sure the green indicator light is bright and steady before you retighten the wingnut. This can take a few attempts before it is back in alignment.
If an indicator light is out on only one of the sensors, check for a possible loose wire. The sensor wires are attached to the white and black terminals on the back or side-panel of the overhead motor unit. Make sure the wires are securely connected to the terminals. If everything looks okay here, check the wires at the sensors. Move the wire around where it is connected in the back of the sensor. If the indicator light comes on, you have a short in the wires and/or sensor, and will have to replace the sensors.
If the problem seems to occur only during the daytime, check to make sure the receiving eye is not in direct sunlight. If this is the case, remount or adjust sensor back toward the side of the garage.
After any adjustment to the sensors, the opener itself or the door, test both reversing systems.
To test the safety sensors with the door open, press the remote control or pushbutton to close the door. Break the beam using your hand or a carton. The door should immediately reverse to a fully open position and the opener bulb will flash 10 times.
Next, place a one inch board (or 2 x 4 laid flat) on the floor, centered under the garage door. Operate the door in the down direction. The door must reverse on striking the board. If it does not, refer to your owner´s manual, call your local LiftMaster Authorized Dealer or speak to one of our technical service representatives by calling our S.O.S. HotLine® at 1-800-528-5880. Failure to pass the above tests could result in serious injury or death.
Please remember to repeat this test once a month.