When snow, ice or frost sits in the beam between the two safety sensors, the opener sees an obstruction and the door will not close or reverses. Clear the beam, wipe both lenses and check the indicator lights. Never bypass or disable the sensors. If the lights stay off or blink after that, call a technician.
1How the sensors work
Two small sensors sit on either side of the door near the floor. One sends a beam and the other receives it. Chamberlain explains that if something crosses the beam while the door closes, the door stops and reverses. Chamberlain says to mount both no higher than 6 inches above the floor, which is low enough to catch a child or a pet but also low enough to be hit by a snow pile.
That is why winter causes trouble. A drift against a sensor, ice on a lens, or a shovel that knocks one out of line can all look like an obstruction.
2What the lights tell you
| What you see | Likely cause | What to do |
|---|---|---|
| Both lights solid | Aligned and working, per Chamberlain's guide for its sensor model | Look for another cause, such as the opener or force settings |
| Receiving light blinking | Misaligned or something in the beam | Clear snow or ice, wipe the lenses, then check alignment |
| Sending light on, receiving light off | Likely a wiring problem at the receiving sensor | Call a technician |
| Both lights off | Likely a wiring problem at the sending sensor, or no power | Check the opener has power, then call |
| Door closes a little, then reverses | The opener senses a blocked beam | Walk the line between the sensors and clear it |
Light meanings vary by brand and model. Check your manual.
3Checks you can do safely
Clear the beam
Remove snow, ice, leaves or stored items between and around the two sensors.
Wipe the lenses
Use a soft, dry cloth. Do not scrape ice off with a tool.
Look at both lights
Compare them with the table above and your manual.
Check the aim
See that each sensor still points straight at the other and was not knocked by a shovel or a bumper.
Realign if needed
Chamberlain's steps: disconnect power, loosen the wing nut on the receiving sensor, point both lenses at each other, tighten when the light glows steadily, then test the door.
4What not to do
They are the part that stops the door from closing on a person, pet or car. Do not tape them, disconnect them or hold the wall button to force the door down. If the door will not close and you cannot fix it in the checks above, leave it and call.
Chamberlain's error code page lists three causes when the opener says the sensors have a problem: blocked, not aligned or a wiring issue. Snow and ice only explain the first two. A wire that is cut or pinched needs a technician.
5Test it once it works
LiftMaster suggests running its safety check on the photo eyes and the auto-reverse before winter. After you clear the sensors, close the door and wave an object across the beam. The door should stop and reverse. See the Illinois maintenance checklist for the monthly test.
6When to call
Call if the lights stay off or blink after the lenses are clear, if the wire is damaged, if the door reverses with a clear beam or if you are unsure which sensor is at fault. Our approved range for sensors, rollers or a tune-up is $150 to $350, depending on the number of rollers, the sensor type and the door size, with the final price confirmed after we see the door. See opener repair and garage door repair.
7Who to call
Emil Garage Doors repairs garage doors, springs, cables and openers and installs new doors in Illinois, including Oak Park, Skokie and Berwyn. Call or send your details and we book the soonest visit.
Questions people ask
What does a blinking garage door sensor light mean?
Usually misalignment or something in the beam. On the Chamberlain model in its guide, a blinking green light means misaligned or obstructed. Clear the beam and check the aim.
How do I fix and test garage door sensors?
Clear snow and ice, wipe the lenses, make sure the lights glow steadily and realign the sensors if needed. Then close the door and wave an object across the beam; it should stop and reverse.
Can snow stop my garage door from closing?
Yes. Snow or ice in the beam, or a sensor knocked out of line, makes the opener think something is in the way, so the door will not close or reverses.
Can I disable the safety sensors?
No. They protect people and pets. Never bypass them. If you cannot clear the fault, stop using the opener to close the door and call a technician.
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Read next
Sources
- Chamberlain support: How to align safety reversing sensors (LED meaning, alignment steps, sensor height)
- Chamberlain support: Garage door safety sensors, error code 1-1 (sensors blocked, not aligned or wiring)
- LiftMaster press release: Ready the garage for harsh winter weather (lubrication, weather stripping, photo eye and auto-reverse checks)