Why does my garage door sensor keep blinking?

Your garage door sensor keeps blinking because it is detecting a problem that is preventing it from maintaining a solid, uninterrupted infrared beam, and the system is designed to blink as a warning code. If the green light on the receiving sensor keeps blinking, the most common reason is chronic misalignment. The sensor brackets are flimsy and located near the floor where they get bumped, so vibration from the door opening and closing can cause them to drift out of alignment repeatedly. Tighten the wing nut securely and ensure the bracket is firmly screwed to the wall, not just the track. Another reason is intermittent obstruction. Spider webs, dust, leaves, or storage boxes that slightly intrude into the beam path will cause blinking. Direct sunlight is a huge culprit, especially in late afternoon when low sun shines straight into the receiving sensor lens and overwhelms the infrared signal, causing blinking only at certain times of day. If the yellow or red sending light keeps blinking, it is usually a loose wiring connection that makes and breaks contact as the door moves or temperature changes. Inspect the bell wire run for loose terminals, staples, and rodent damage.