Garage Door Sensor Not Working? How to Find the Problem
Updated November 2026 · Part of our garage door safety guides
When a garage door will not close, or closes and then reverses, the safety sensors are the usual suspect. They are also the easiest part of the system to troubleshoot yourself, as long as you know what you are looking at. This guide walks through the fault in the order a technician would check it.
Need it fixed instead? Our garage door sensor repair page explains what we do on a visit, and we can often tell you the likely cause from a description over the phone.
What Do Garage Door Sensors Do?
Two small units, called photo eyes, sit a few inches above the floor on either side of the door. One sends an invisible beam and the other receives it. If something breaks the beam while the door is closing, the opener reverses. If the units cannot see each other at all, many openers refuse to close the door. That is why a sensor fault looks like a door problem.
Step 1: Watch What the Door Does
The way the door fails narrows the cause before you touch anything.
| What you see | What it points to |
|---|---|
| The door will not close and the opener light blinks | Sensors blocked, misaligned or without power |
| The door starts down, then reverses | The beam is broken partway, or a limit, force or track issue |
| The door closes only while you hold the wall button | The sensors cannot see each other, or one has failed |
| It works in the morning and fails late in the afternoon | Sunlight shining into the receiving lens |
| The door works but one sensor light is dark | A wire or a sensor on that side has failed |
Step 2: Read the Lights
Each sensor has a small indicator light. On many LiftMaster and Chamberlain openers, the sending eye shows an amber light and the receiving eye shows a green one, though colors vary by brand, so check your manual. With the beam clear, both lights should be solid.
- Both solid: the beam is fine, so look at limits, force and the track instead
- One dark: that unit has no power, or its wire is damaged
- Both dark: the sensors are not getting power, so check the opener and the wiring
- Flickering or dim: a loose connection, a poor splice or moisture
Step 3: Clear and Clean
- Move anything stored near the floor on either side of the door
- Wipe both lenses with a soft, dry cloth
- Look inside the housings for cobwebs, insects and dirt
- Remember that humid South Florida mornings can leave a film on a lens
Step 4: Realign the Sensors
- Loosen the bracket just enough to move the unit by hand
- Aim it at the other sensor until its light turns solid
- Tighten the bracket without moving the aim
- Check that both units are at the same height and no higher than six inches above the floor
- Test the door with a clear path
Step 5: Check the Wires
Follow each wire from the sensor along the wall and ceiling to the opener. Look for staples that pinch the wire, chewed spots, kinks and loose splices. Unplug the opener before you touch anything at its terminals, and if you are not sure what you are looking at, stop and call.
Step 6: Rule Out Sunlight
Strong sunlight shining straight into the receiving lens can swamp the beam for a short window each day. If the door only fails at one time of the afternoon, shade the lens with a small hood or shield and test again. Our sensor repair page covers this in more detail.
Step 7: Power-Cycle the Opener
Sensors have no reset button. Resetting them means realigning the units and, if needed, unplugging the opener for about thirty seconds before plugging it back in. That clears minor glitches and gives the opener a fresh start.
Step 8: Test the Result
Close the door with a clear path and watch it complete the cycle. Then test the safety reversal, as our guide to testing your garage door’s safety features explains. If the door passes, you are done.
When Should You Stop and Call a Technician?
- The lights stay dark after you have checked the opener’s power
- A wire is damaged, buried in a wall or spliced
- Both sensors are dark
- The door still reverses with both lights solid
- The opener has no sensors at all, which means it predates 1993
- You are not sure what you are looking at
What not to do
- Do not tape over a sensor or disconnect it
- Do not hold the wall button down as a permanent fix
- Do not open the opener housing
Bypassing the sensors removes the protection that stops the door on a child, a pet or a bumper.
Related Services and Guides
- Garage door sensor repair, what we do on a sensor visit
- Opener repair, for faults beyond the sensors
- Opener installation, if your opener is too old for current sensors
- How to test your garage door’s safety features
- LiftMaster vs. Chamberlain, for sensor light colors by brand
- Garage door won’t close all the way or stops partway
- Garage door opener beeping or blinking: what it means
Frequently Asked Questions
Why is only one of my garage door sensor lights on?
One dark light means that unit has no power, or its wire is damaged, or the unit itself has failed. Follow the wire from the dark unit to the opener and look for damage. If you cannot find it, call.
Can weather affect garage door sensors?
Yes. Humidity can leave a film on the lens, heavy rain can knock a bracket out of line, and low sun can swamp the receiving eye. Wiping the lenses and checking the alignment after a storm solves many problems.
Can I replace just one sensor?
Sometimes, but sensors are usually replaced as a matched pair for the opener, and the wire is checked at the same time. A technician can tell you which applies.
Is it safe to close the door by holding the wall button?
Many openers allow it, but it turns off the safety reversal while you hold it. Use it only as a short-term way to close the door, and get the sensors repaired.
Sensor still not working?
Describe what the door is doing, and we will tell you the likely cause and how soon we can be there.
Elite Miami Gardens Garage Door Repair, 6187 NW 167th St, Suite 101, Miami Gardens, FL 33014