Updated October 2026
Short answer
A Houston garage door that starts down and reverses, with the opener light blinking, almost always has a safety sensor problem: the photo-eyes are out of line, dirty, blinded by sun or have a damaged wire. Realignment is often quick; a broken sensor or cut wire needs replacing.
Signs of a sensor problem
The door reverses near the floor
The beam is being broken or lost.
The opener light blinks
Many openers flash a code for sensor faults.
It only fails in the afternoon
Sun glare on one sensor.
It closes only if you hold the button
The opener is overriding a sensor fault.
One sensor light is out
Wiring or a failed sensor.
How a sensor repair runs
Read the opener
Diagnostic flashes and sensor lights checked.
Check alignment and lenses
Brackets tightened, lenses cleaned.
Test the wiring
Run traced and tested end to end.
Repair or replace
Wiring repaired or matched sensors fitted.
Auto-reverse test
Beam broken mid-close, door must reverse.
What the safety sensors do
Every residential opener sold today uses a pair of photo-eyes mounted a few inches above the floor on each side of the door. One sends an invisible beam, the other receives it. If anything breaks the beam while the door is closing, the opener reverses.
When the opener cannot see the beam at all, it refuses to close and usually blinks its light to tell you why. LiftMaster, Chamberlain and Genie openers each signal sensor faults differently, and reading that signal is the first step.
Blinking sensor light
Most sensors have a small indicator light. A solid light on both usually means the beam is working; a blinking or dark light on one side points to misalignment or a wiring fault. A bracket knocked by a bin or a bicycle is the most common cause. Realigning it until both lights are steady often fixes the problem, but we also tighten the bracket, so the next bump does not undo the fix. If the lights flicker rather than stay dark, the wiring is a more likely culprit than the alignment, and we test it before adjusting anything.
Sun glare on west-facing doors
Late-afternoon sun shining straight into the receiving sensor can blind it, so the door works in the morning and refuses to close at 5 p.m. The fix is usually swapping the sensors side to side so the receiver faces away from the sun, or fitting a sun shield. It is a simple fix once you know the cause, which is why we ask what time of day the problem happens. Tree shade, a parked car or a reflective trash can lid can play the same trick at certain times of day, so we look for those too.
Damaged sensor wiring
Sensor wires run along the wall and up to the opener, and they get stapled through, chewed or pinched by shelving. A damaged wire gives intermittent faults that come and go with temperature or vibration. We test the run, replace damaged sections or the whole run, and replace the sensor pair if a lens is cracked or a unit has failed, then test the auto-reverse. Sensor wiring that runs along the floor is also easy to catch with a broom or a shelf, so we route the new run up and out of the way, secured with insulated staples rather than staples driven through the wire.
Sensor checks you can do yourself
Sensor problems are one of the few opener faults that homeowners can often fix safely.
| Task | Doing it yourself | Why we handle it |
|---|---|---|
| Wipe both lenses | Safe. | Dust and cobwebs can block the beam. |
| Clear anything near the beam | Safe. | A bin or broom handle will stop the door. |
| Gently realign a bumped bracket | Safe. | Aim for solid lights on both sensors. |
| Bypass or remove the sensors | Never. | They are the main safety device on the door. |
| Splice damaged wiring | Leave it to us. | Loose splices cause intermittent faults. |
Why afternoon sun trips Houston sensors
Houston's long, bright afternoons are hard on garage door sensors on west-facing driveways, because the low sun shines straight into the receiving eye at the end of the day. Doors that close fine every morning and reverse every evening are usually that, not a broken opener. Swapping the sensors side to side or adding a sun shield is often the whole fix, which is why we ask when the problem shows up before we come out.
Brands we service and install
We repair sensors on LiftMaster, Chamberlain, Genie and Craftsman openers, and replace them with matched pairs for the opener brand.
What drives the cost of a sensor repair
Sensor work is usually one of the smaller opener jobs. What it costs depends on whether anything needs replacing.
- 1
Realignment only. Quickest and least expensive.
- 2
Wiring. Damaged runs are repaired or replaced.
- 3
Sensor replacement. Matched pairs for the opener brand.
- 4
Opener age. Very old openers may not take current sensors.
- 5
Underlying faults. A logic board fault is priced separately.
Questions about this job
Garage door sensor questions
Usually the safety sensors: they are out of line, dirty, blinded by sun or have a wiring fault.
Loosen the bracket, aim the sensors at each other until both lights are solid, and tighten it again.
Low sun shining into one sensor can blind it. Swapping sides or a sun shield usually fixes it.
No. They are the main safety device that stops the door closing on people and pets.
Yes, replacement sensors should be matched to the opener.
Many openers let you override a sensor fault by holding the button. It means the sensors need attention.