A blinking garage door sensor light usually means the two photo eyes are misaligned or something is blocking the beam. On Chamberlain and LiftMaster sensors, a blinking green light points to misalignment or an obstruction, and two steady lights mean the pair is aligned. Clear the beam, clean the lenses and realign them. If the lights stay off, call.
What the lights are telling you
The two safety sensors sit on either side of the door near the floor. One sends an invisible beam and the other receives it. If the beam is broken, the opener will not close the door. On the Chamberlain sensors described in the company's support article, the amber light is the sending sensor and the green light is the receiving sensor.
- Green light blinking: the sensors are misaligned or something is in the way.
- Both lights solid: the sensors are aligned and working.
- Both lights off: a wiring problem with the sending sensor.
- Amber on, green off: a wiring problem with the receiving sensor.
Your opener may also tell you. On many LiftMaster openers the main lights flash 10 times when there is a sensor problem, and twice when the wall control LOCK button is on.
Check these before you touch anything
- Look for a box, bag, bike or tool leaning into the doorway and move it.
- Wipe both lenses with a soft cloth.
- Check that the sensors are mounted no higher than 6 inches above the floor, one on each side of the door.
- Look at the receiving sensor. Direct sunlight can block the signal from the sending sensor, so notice whether the sun hits it.
How to realign the sensors, step by step
Unplug the opener
Chamberlain says to disconnect power before installing or adjusting sensors. Unplug the opener or turn off its breaker.
Clear the doorway
Make sure nothing blocks the beam between the two sensors.
Loosen the receiving sensor
Loosen the wing nut on the receiving sensor, the one with the green light.
Aim the lenses at each other
Point the two lenses directly at each other. A sensor that has been bumped is often only turned a little.
Tighten and check the lights
Tighten the wing nut once the green light glows steadily. Restore power and confirm both lights are solid.
Test the door
Close the door with the remote or wall control, then do the reverse test in garage door safety tests.
Small turns are enough. If the lights do not both stay solid, loosen both sensors, realign them and test again.
What not to do
- Do not tape over a sensor, unplug it or bypass it to get the door to close. The sensors are what stop a door that meets a child, a pet or an object.
- Do not raise the opener's force setting to push through a problem. Chamberlain advises using only the minimum force needed to close the door.
- Do not skip the reverse test after an adjustment. Chamberlain says it should be done monthly, and the door must reverse on a 1-1/2 inch object laid flat on the floor.
When the lights stay off or keep blinking
If realigning does not help, the cause is often outside the sensor. On some LiftMaster openers, arrow lights that show one up and one down mean the sensor wires are cut or disconnected, and one up and two down means they are reversed or shorted. Wiring and sensor replacement are jobs for a technician.
A door that will not close may also have a travel, balance or binding problem. Chamberlain lists an unbalanced door among the common causes. See why a garage door will not close.
Get the sensors checked
Our typical price for rollers, sensors or a tune-up is $150 to $350, and we confirm the final price after we see the door. We repair openers and sensors across Southern California, for example in Adelanto, Agoura Hills and Arcata. Call (213) 340-4232 or use the estimate form, and see opener repair.
Questions people ask
What does a blinking garage door sensor light mean?
It usually means the sensors are misaligned or the beam is blocked. On Chamberlain sensors, a blinking green light points to misalignment or an obstruction.
How do I fix and test garage door sensors?
Clear the path, clean the lenses, loosen the receiving sensor, point both lenses at each other and tighten it when the light is steady. Then close the door and run the reverse test.
Can sunlight make my garage door sensor blink?
Yes. Chamberlain says direct sunlight on the receiving sensor can block the signal from the sending sensor.
Why won't my garage door close when the sensor light is blinking?
The opener treats a broken beam as an obstruction and will not close the door. Realign the sensors first.
Services that fit this problem
Garage door and gate help near you
We repair and install in these cities. Each page has local notes, prices and reviews.
More guides
Sources
- Chamberlain Group support: Why do the lights on my garage door opener flash and my door will not close
- Chamberlain Group support: How to align safety reversing sensors
- Chamberlain Group support: Why won't my garage door fully close
- Chamberlain Group support: How do I test the Safety Reversal System
- Chamberlain Group support: How do I install my safety reversing sensors in a pre-wired garage