All overhead door openers produced after January 1, 1993 include the federally ordered safety sensor auto reversing system. These sensors are found four to six inches on top of the garage floor and safeguard the door opening with an invisible beam. If there is any problem with the safety sensors, the light bulb on some openers will flash many times and the garage door will not close unless steady pressure is used to the wall button mounted inside the garage.
There are a some different things that can cause this type of issue, which are listed below with similar solutions:
1. Clear any obstruction from between the safety sensors. Debris from leaves, trash, and dirt on the lens of the safety eye itself are all examples of things that can hamper the sensor’s signal.
2. Check each sensor for a steady glowing indicator light. If both indicator lights are on, or if one indicator light is flickering, the sensors may be slightly out of alignment.
To check for misalignment; block the beam of the sensors so that they cannot directly see each other. When the safety eyes is blocked, the indicator light on one of the two sensors will briefly go out. This is most likely receiving sensor. Eliminate the obstruction and loosen the bracket on the back of the receiving sensor. Adjust the receiving sensor until the indicator light goes out, if not already out, then realign until the green or red light is bright and steady, then refasten the sensor. This usually takes a couple of trys before it is back in alignment.
If an indicator light is not glowing on one or both sensors, check for a possible loose or shorted wire. Sensor wires are hooked to the white and black terminals on the back or side 10X10 Garage Door Kit panel of the overhead motor unit. Confirm that they are securely connected to each terminal. Also confirm the wires for any breaks, usually anywhere they are spliced together.
If the above steps have been followed carefully and the symptoms continue, there may be an electronic short in either the wiring, safety eyes, or the receiver logic board. In this case, remove the safety beams and temporarily wire them in the motor head unit with a shorter known unshorted set wires. Should the symptoms continue after the eyes are removed, replace the circuit board and or safety beams. If the symptoms stop with the safety beams after using unshorted wires to the opener unit, reinstall all the wiring from the motor head to the safety sensor location 4 to 6 inches on top of the floor.
Following any adjustment to the sensors, the unit itself, or the garage door, the safety system must be tested:
1. Activate the remote control push button to raise the garage door.
2. Put a box or similar object in the path of the door.
3. Activate the remote control push button to lower the door. The door will not move more than one inch, and the opener lights will flash.
WARNING: Without a properly equipped safety reversal device, persons (particularly small children) can be threateningly injured or death by a closing overhead door. If the motor Garage Repair Contractors unit closes the door when the safety-reversing sensor is obstructed (and the sensors are no more than 6 inches on top of the floor), call for a trained door systems technician.

By master