Why is my sensor blinking red?

Your sensor blinking red is most commonly seen on Genie, Overhead Door, and some older Stanley garage door openers, where red is used for the sending sensor. A solid red light means the sensor has power and is working, but a blinking red light means there is a fault preventing it from sending a stable beam. The most likely cause is a wiring issue between the sensor and the garage door opener motor unit on the ceiling. The low-voltage wire that powers the sensors can become loose at the terminal screws on the motor head, or it can be damaged by a staple driven too tight, a nail, or rodent chewing in the garage attic. When the wire has an intermittent connection, the power flickers and the red light blinks. Another cause is a power surge or a failing circuit board in the opener that can no longer supply consistent power to the safety circuit. Less commonly, moisture has gotten inside the sensor housing and corroded the electronics, which happens in garages that get wet or have poor sealing near the floor. Start troubleshooting by unplugging the opener for 30 seconds, checking the wiring connections at both ends, and cleaning the sensor. If it still blinks red, replace the sensor pair.