Applicable: This safety sensor is applicable to Master Mechanics& (since 1997) Function: The security sensor sends an light inside the garage door. Whenever there is an obstacle, the garage door automatically reverse before causing any damage to prevent accidents Replacement: 041A5034 Replacement of safety sensor: G801CB-P, 2610459, 012381050345, 041A5034 Under what circumstances should it be replaced: 1. There is no obstacle, but the garage door stops backing 2. The green light is on, but the yellow light is not, please replace the sensor 3. In cold weather and strong ultraviolet light, the garage door stops reversing, Manufacturer: CTRLZS