01Common causes
Dirty lenses, a sensor knocked out of line by a bike or a broom, loose brackets, damaged low-voltage wire, and low-angle sunlight shining into one eye. Indicator lights on the sensors usually show whether they see each other.
02Simple checks first
Clear anything in the door path, wipe both lenses, and look at the lights. If one is off or blinking, gently align the bracket until it is steady. If the door still will not close, the wiring or the sensor itself may be failing.
03What a tech does
The tech checks voltage at the opener, traces and repairs the wire, realigns or replaces the sensor pair, and then runs the auto-reverse test with an object on the floor. Older or failing opener boards are covered on opener repair.
04Do not bypass them
Taping sensors together or mounting them high defeats the point; they are there to stop a closing door from hitting a child, pet or car. If you need to close a door with a dead sensor, use the wall button held down only as your manual allows, and book a repair.
05Related problems
A door that reverses even with good sensors may have a force setting, track or spring problem; see off-track door repair and spring repair.
