--- title: "Garage Door Sensor Not Working? Here's How to Read the Lights" page_title: "Garage Door Sensor Not Working? Read the Lights by Brand" description: "Sensor light off, blinking, or the wrong color? Read what each state means by brand, fix the common causes, and know when a photo eye has actually failed." url: "https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-sensor-not-working/" type: "opener-symptom" published: "2026-09-01T19:29:18Z" modified: "2026-09-01T19:37:13Z" publisher: "Farnsworth Garage Door Service, Mesa, AZ" phone: "(602) 935-9766" --- # Garage Door Sensor Not Working? Here's How to Read the Lights Those two small units bolted near the floor on either side of your door opening are the safety sensors — photo eyes, if you want the trade name. One shoots an invisible infrared beam across the opening and the other watches for it. Break that beam and the opener refuses to close, by design and by federal law. The genuinely useful thing about them is that they tell you what's wrong through their indicator lights, and once you know how to read those lights you can usually diagnose the problem in under a minute. This page covers what every light state means on every major brand, what causes each one, and how to tell an alignment problem from a sensor that's actually dead. ✓ **Basic check — low risk** Looking, cleaning, clearing, and adjusting by hand. Nothing here is under tension. This is general guidance based on what we see on service calls — it isn’t a substitute for someone looking at your actual door. Every door is a little different, and if anything here feels beyond what you want to take on, stop and [give us a call](tel:+16029359766). Start Here ## What to check in the next 10 minutes Start here. Most sensor problems are solved by one of these four, and none of them takes more than a couple of minutes. 1. 1 **Look at both lights and note exactly what each is doing** On, off, dim, steady, or blinking — and what color. Those two data points are most of the diagnosis. Don't skip straight to adjusting; read them first. You’ll know it worked when: You can describe both sensors: “left one steady green, right one off,” for example. 2. 2 **Clear the beam path** Anything crossing the line between them counts — a bin, a hose, a bag of soil, a bike wheel, a broom handle. The beam sits about six inches off the floor and it's completely invisible. You’ll know it worked when: There's clean floor between the two sensors with nothing crossing it. 3. 3 **Wipe both lenses with a dry cloth** No solvents — they haze the plastic. Around here they build up a film of fine dust you honestly can't see until you wipe it and look at the cloth. Spider webs are the other common one; they love the warm housing. You’ll know it worked when: Both lenses are visibly clear and both lights stayed on while you cleaned. 4. 4 **Re-aim whichever one is misbehaving** Loosen the wing nut just enough to pivot it, aim it straight at its partner, and watch the light. When it goes solid and stays solid, tighten it back down without letting it drift. You’ll know it worked when: Both lights are steady and the door closes with the remote. ## Is it really the sensors? Worth confirming before you spend time on them, because a couple of other faults look identical from the driveway. Press and **hold** the wall button. Does the door close all the way while you keep holding it down? Yes — it closes while I hold it **What that means:** Confirmed: it's the sensors. Holding the wall button is the deliberate override that bypasses the safety circuit, so if that's the only way it closes, the opener isn't getting a satisfactory signal from the photo eyes. Everything on this page applies to you. **Where to go next:** Read the light guide below and find your combination. No — it won't close either way **What that means:** Not the sensors. The opener is refusing for a different reason: a travel limit or force setting, something binding in the track, or a problem with the door itself. The sensor lights might look wrong as a red herring. **Where to go next:** Go to our full [won't-close guide](https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-wont-close/), which covers all eleven causes. Use the hold-the-button override once, to diagnose, with a clear view of the doorway. It switches off the system that stops the door on a child or a pet, so it isn't something to live with. ## Which light problem do you have? Each of these points somewhere different. Find yours. One light off, other steady Power or wiring problem on the dead side, or that sensor has failed. Not usually alignment — a misaligned sensor still lights up. [Jump to that fix ↓](#cause-2) One light blinking Classic misalignment or a blocked beam. The receiver can see something but not cleanly. [Jump to that fix ↓](#cause-1) Both lights off No power reaching either sensor. Look at the opener end, not the sensors. [Jump to that fix ↓](#cause-2) Both steady but door still won't close The sensors are fine. Something else is stopping the door. [Jump to that fix ↓](#cause-6) Lights fine in the morning, trouble in the afternoon Sunlight washing out the receiving eye. Very common on west-facing garages here. [Jump to that fix ↓](#cause-4) Works some days, not others Intermittent — usually a partly broken wire flexing with temperature, or a loose terminal. [Jump to that fix ↓](#cause-3) ## How the sensors actually work There are two units and they do different jobs, which is why their lights behave differently and why swapping them around is sometimes a legitimate fix. The **sending** eye does one thing: emit a beam of infrared light. Its indicator is usually amber or yellow, and it stays lit whenever the sensor has power. It doesn't know or care whether anything is receiving. The **receiving** eye is the one doing the thinking. Its indicator — usually green — stays steady when it can see a clean beam from its partner, and it blinks or goes out when it can't. It's also the one that gets fooled by direct sunlight, because it's looking for a specific infrared signal and bright sun floods it with infrared noise. That's why a dead sending eye and a blocked beam produce different light patterns, and why knowing which one is which cuts your troubleshooting in half. If the amber light is out, that sensor has no power. If the green light is blinking, the receiver has power but isn't happy with what it's seeing. **Sending eye** Emits the beam. Amber or yellow light, on whenever it has power. **Receiving eye** Watches for the beam. Green light, steady when the path is clear. **Steady vs blinking** Steady = happy. Blinking = has power but can't see the beam properly. **Light off entirely** No power reaching that sensor — wiring, terminal, or a failed unit. **Bracket** The thin metal clip holding the sensor. Bends easily, which is why they drift. **UL 325** The safety standard requiring the opener to refuse to close unless it can confirm the beam. One useful consequence: if you swap the two sensors side for side and the problem follows the sensor, that sensor is faulty. If the problem stays on the same side of the garage, it's the wiring on that side. ## The light guide Find your combination. Colors vary slightly by brand — the brand tables further down have the specifics. | What you’re seeing | Most likely cause | How urgent | Who should fix it | | --- | --- | --- | --- | | **Both lights steady** | Sensors are healthy — the fault is elsewhere | Look elsewhere | You can do this | | **Receiving light blinking, sending steady** | Misaligned, dirty lens, or something in the beam | Fix today | You can do this | | **Receiving light off, sending steady** | Wiring fault on the receiver side, or failed receiver | Fix this week | Either — call us if unsure | | **Sending light off, receiving on** | No power to the sender — wiring or failed unit | Fix this week | Either — call us if unsure | | **Both lights off** | No power from the opener — terminal, board, or a shared wire fault | Fix this week | Call a pro | | **Light flickers when you touch the wire** | Broken conductor inside the insulation | Fix this week | Either — call us if unsure | | **Steady all morning, blinking by late afternoon** | Low sun blinding the receiver | Fix this week | You can do this | | **Lights fine but opener blinks 10 times** | Opener isn't seeing the sensor signal despite the lights | Fix today | Call a pro | ## What’s actually causing it These are ordered the way we work through them on a real service call — cheapest and most common first, so you don’t start by replacing a part that was never the problem. 1 ### One or both sensors have drifted out of alignment Basic check The single most common cause, and the easiest to fix. The sensors sit low in a busy garage on thin metal brackets that bend if you so much as lean a rake against them. A car door, a bike, a kid's scooter, or just years of the door cycling and vibrating the wall will nudge one a few degrees off — and a few degrees is enough over that span. How you can tell: The receiving light blinks rather than holding steady. The sending light is usually fine. The fix 1. Work out which sensor is the receiver — it's the one with the blinking light. 2. Loosen its wing nut or bracket screw just enough that the sensor pivots with gentle finger pressure. You don't need to remove anything. 3. Slowly aim it toward its partner while watching the indicator. 4. When the light goes solid and stays solid for a few seconds, hold that position. 5. Tighten the bracket without letting the sensor rotate as you go. 6. Test with the remote rather than the wall button, so you're not accidentally using the hold override. You’ll know it’s right when: Both lights are steady, and they stay steady when you gently tap the wall nearby. **Where to stop:** If you can't get a steady light at any angle, stop adjusting — the problem isn't aim. Move on to the wiring and power causes below. 2 ### A sensor has lost power Hands-on — moderate risk A sensor with no light at all is not an alignment problem. It's either not receiving power, or the unit has failed. The two are worth telling apart before you buy anything, because a new sensor won't fix a broken wire. How you can tell: One light completely off — not dim, not blinking, off — regardless of how you aim it. If both are off, suspect the opener end rather than the sensors. The fix 1. Check both wires where they land at the opener's terminal block. A wire that's worked its way out of a terminal is extremely common, and it's a thirty-second fix. 2. Look at the terminal screws for corrosion — a green or white crust means a poor connection. 3. Swap the two sensors side for side, leaving the wiring where it is. If the dead light moves to the other side of the garage, the sensor is faulty. If it stays put, the wiring on that side is at fault. 4. If you find a wire that's obviously cut or crushed, that's your answer. You’ll know it’s right when: Both sensors light up steadily once the connection is restored. **Where to stop:** If both lights are dead and the terminals look fine, don't keep poking — that points at the opener's logic board, and the board is the most expensive part in the unit. Worth a call rather than a guess. Board diagnosis is part of a [garage door opener repair](https://farnsworthgarage.com/garage-door-repair-service-installation/garage-door-motor-opener-repair-replacement-installation/) and it saves buying parts on spec. 3 ### The sensor wire is nicked, pinched, or chewed Hands-on — moderate risk Sensor wire is thin two-conductor stuff stapled along the wall and run back up to the opener. It gets caught by shovels, pinched behind shelving, punctured by a staple during some other project, and gnawed by rodents. When only part of the conductor is broken, the fault comes and goes as the wire flexes or as the garage heats up and everything expands — which is why this one so often presents as “it works some days.” How you can tell: An intermittent fault with no pattern you can pin down, or a light that flickers when you wiggle the wire. The fix 1. Follow each wire from its sensor all the way back as far as you can see it, looking for cuts, staple punctures, kinks, crushing, or green corrosion. 2. Pay particular attention where the wire turns a corner, passes a stud, or runs near anything mounted to the wall since the opener was installed. 3. Gently flex the wire along its run while watching the sensor light. A flicker means you've found the break. 4. Check the last few inches at both ends — the sensor pigtail and the opener terminal — where flexing is worst. You’ll know it’s right when: The light stays rock steady while you flex the whole run. **Where to stop:** Splicing low-voltage sensor wire is within reach for most people, but if the damage is inside a finished wall, or you're not confident which terminal is which at the opener, call us. Reversing those wires or shorting them can take out the logic board. 4 ### Direct sunlight is blinding the receiving eye Basic check Nothing is broken in this one, which is why it confuses people. The receiving eye is looking for a specific infrared signal, and low direct sun floods it with infrared until it can't pick the beam out of the noise. The opener reads that as a blocked beam. It's genuinely common in the Phoenix area, and it tends to appear seasonally as the sun's angle changes rather than all at once. How you can tell: The door behaves perfectly in the morning, gets stubborn in the late afternoon, and is fine again after dark. Usually a west-facing garage, usually worse in winter when the sun sits low. The fix 1. Note the time of day it fails, then go and look at whether direct sun is falling on either sensor at that hour. 2. Test it: shade the receiving sensor with your hand or a bit of cardboard and try the door again. If it closes, you've found it. 3. For a permanent fix, fit a small hood over the receiving eye — a purpose-made shield, or a short length of PVC pipe split lengthwise works fine. 4. Alternatively, swap the two sensors side for side so the receiver faces away from the afternoon sun. You’ll know it’s right when: The door closes normally at the hour it used to fail. **Where to stop:** If none of that helps, this isn't your cause and the next one is worth a look. 5 ### The sensor itself has failed Hands-on — moderate risk Sensors do eventually die. They live near the floor in a garage that hits 130°F-plus in summer, they get splashed, and the plastic housing seals degrade. Twenty years is a good run. Once the internals go, no amount of cleaning or aiming will bring the light back. How you can tell: You've confirmed the wiring is sound and the terminals are clean, and swapping the sensors side for side made the fault follow the unit. The fix 1. Confirm with the swap test before buying anything — it's the difference between a cheap part and a wasted afternoon. 2. Look for moisture or condensation inside the lens, which means the housing seal has failed. 3. Replace sensors as a matched pair from the same manufacturer as your opener. Mixing brands or generations is a common source of new problems. 4. Note your opener's brand and model before ordering — sensor compatibility isn't universal even within one brand. You’ll know it’s right when: The new pair lights steady and the door closes normally. **Where to stop:** If you'd rather not source and match the parts, this is a quick and inexpensive job for us, and we'll test the whole safety circuit while we're there rather than just swapping the part. 6 ### The lights look fine but the opener disagrees High risk — call a technician Occasionally both sensor lights are perfectly steady and the opener still throws its sensor fault — ten blinks on a LiftMaster or Chamberlain, for instance. That means the sensors are powered and aligned but the signal isn't arriving at the logic board in a form it accepts. Usually that's a partly failed board input, a wiring fault that's shorting rather than breaking, or a mismatched aftermarket sensor that lights up but doesn't speak the right protocol. How you can tell: Two steady lights, and an opener that still refuses and reports a sensor code. **Where to stop:** This is where homeowner troubleshooting genuinely runs out of road. The remaining possibilities all sit inside the opener, and diagnosing a board input needs a meter and knowing what the correct signal looks like for your model. Give us a call — it's a straightforward diagnosis with the right equipment, and it saves you buying parts on a guess. ## What your opener is telling you, by brand ### LiftMaster & Chamberlain Same parent company, same behavior. The opener's main light also flashes a diagnostic code, which is worth reading alongside the sensor lights. | What you see | What it means | What to do | | --- | --- | --- | | **Green** | Billion Code, 390 MHz — the older system | Billion Code remotes, or consider upgrading the opener | | **Green** | Billion Code, 390 MHz — the older system | Billion Code remotes, or consider upgrading the opener | | **Amber off** | Sending eye has no power | Check its wiring and the terminal at the opener | | **Opener light blinks 10×** | Sensor fault — the most common code these units throw | Work through causes 1 to 3 above | | **Opener light blinks 1× or 2×** | Sensor wire disconnected (1) or shorted (2) | Inspect the wire run and both terminals | | **Opener light blinks 4×** | Sensors slightly out of line, beam briefly interrupted | Re-aim both until the indicators are rock steady | ### Genie Genie calls the system Safe-T-Beam, and it reports through two LEDs on the sensor housings. Note the last row especially — it looks like a sensor fault and isn't one. | LED state | What it means | What to do | | --- | --- | --- | | **Both LEDs steady** | System healthy | Look elsewhere for the fault | | **Receiving LED blinking** | Beam blocked or sensors misaligned | Clear and re-aim until steady | | **Receiving LED off** | No power to the receiver, or failed unit | Check wiring, then swap-test the sensors | | **Sending LED off** | No power to the sender | Check its wiring back to the opener head | | **Both LEDs steady red** | Travel limits were never set or have been lost — NOT a sensor fault | Re-run the limit-setting routine from your manual | ### Craftsman & older units Most Craftsman openers were built by Chamberlain and share the codes above. Genuinely old units may have no diagnostic blink at all. | What you see | What it means | What to do | | --- | --- | --- | | **No diagnostic blink on the opener** | Pre-diagnostic-era unit | Read the sensor LEDs directly and use the swap test | | **Dim rather than off** | Weak connection or a sensor on its way out | Clean the terminals first, then plan on replacing the pair | | **No sensors fitted at all** | Opener predates the 1993 requirement | Strongly worth replacing — it lacks entrapment protection entirely | ## What you’ll need if you’re doing this yourself - **A flashlight** — sensor LEDs are dim and the brackets sit in shadow - **A soft dry cloth** — for the lenses — no solvents, they haze the plastic - **A 7/16-inch or 1/2-inch wrench or nut driver** — most sensor brackets use one of these - **A stepladder** — for reaching the opener head and its terminal block - **A scrap 2x4** — for the safety reversal test afterwards — don't skip it ## Things not to do — and why × Don't bypass, jump, or disconnect the sensors They've been required on every residential opener sold in the US since 1993, and an opener built to UL 325 won't run properly without them anyway. They're the system that stops the door on a child or a pet. Replacing a failed pair is a small job. × Don't tape the wall button down as a workaround Holding the button bypasses the safety reversal deliberately. A taped button is a door that will close on anything in its path, unattended, with nothing to stop it. × Don't clean the lenses with solvent or glass cleaner It hazes and crazes the plastic, which scatters the beam permanently. A dry cloth is all they need. × Don't mix sensor brands or generations A sensor from a different manufacturer may light up convincingly and still not speak your opener's protocol. Replace as a matched pair from the same brand as the opener. × Don't force a bent bracket back into shape repeatedly Thin metal that's been bent and straightened a few times fatigues and snaps, usually taking the sensor's pigtail with it. If a bracket won't hold aim, replace it. × Don't skip the 2x4 test after any sensor work Getting the lights steady tells you the beam is intact. It doesn't confirm the opener will actually reverse on an obstruction — that's a separate check, and it's the one that matters. × Don't raise a sensor bracket to get it clear of something It's the obvious fix when a recycling bin or a bike pedal keeps clipping the beam, and it quietly defeats the device. Six inches above the floor is the maximum beam height in DASMA's inspection checklist, in DASMA's opener guide and in LiftMaster's manual alike. Move whatever is in the way instead — the beam is meant to be low enough that a child lying in the doorway breaks it. ## Why sensors give more trouble here Photo eyes have a harder life in the Phoenix area than they do most places, and it shows up in the call volume. The sun is the big one. Our sensors sit low and face straight across the opening, and on a west-facing garage in winter the late-afternoon sun can shine directly into the receiving eye and swamp the beam. Nothing is broken — the sensor simply can't pick the signal out of the glare. If your door is reliable all morning and difficult around four or five, that's almost certainly what you're looking at. - **Afternoon-only faults** — low sun blinding the receiver. Shade the eye or swap the sensors side for side. - **Post-monsoon dust** — fine silt films the lenses in a way ordinary dirt doesn't. It doesn't look dirty until you wipe it and check the cloth. Worth adding to your after-storm walkaround. - **Heat and brackets** — a closed garage here runs well past 130°F in summer and everything expands. Brackets that were dead-on in March can sit a few degrees out in July. - **Wire insulation** — years of heat cycling makes thin sensor wire brittle, so nicks that would have been harmless elsewhere eventually open up into intermittent faults. - **Housing seals** — UV and heat degrade the plastic seals, which is why we see condensation inside sensor lenses on older units here more than you'd expect in a dry climate. ## Keeping them working Sensors are low-maintenance, but a few minutes twice a year prevents most of what we get called out for. - **Wipe both lenses twice a year** and always after a dust storm. Ten seconds, and it's the single highest-value thing on this list. - **Keep a clear zone around each sensor** — nothing stored within a foot, so a shifting bin or a leaning tool can't drift into the beam. - **Check the lights every few months** — just glance at them. A sensor that's started blinking intermittently is telling you something before it strands you. - **Shade west-facing sensors before summer** if you've ever had an afternoon fault. Much easier than diagnosing it again next year. - **Run the 2x4 reversal test twice a year** — steady lights don't prove the door will actually reverse on an obstruction. - **Look at the wire run occasionally** especially after any project that involved the garage walls. ## Where this fits A sensor fault is usually self-contained, but it's worth knowing what it's often confused with. Sensor light problem *(you are here)* → [Door won't close](https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-wont-close/) → [Door reverses partway](https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-keeps-going-back-up/) If the sensors check out clean and the door still won't close, the cause is somewhere else entirely — travel limits, force settings, the track, or the door's balance. Our won't-close guide covers all eleven possibilities. ## When to call us Call if both lights are dead and the terminals look fine, if the lights are steady but the opener still reports a sensor fault, if you've found wire damage inside a wall, or if you'd simply rather not spend the afternoon on it. It's a quick job for us and an inexpensive one. What we do on a visit for this - Test both sensors and their full wire run end to end, including the terminals at the opener head - Read whatever diagnostic code the opener is reporting and interpret it for your exact model - Check the signal actually arriving at the logic board, not just the lights on the sensors - Replace sensors or brackets as a matched pair if that's what it needs - Run the safety reversal test the way UL 325 requires and show you the result - Check the door's balance and travel while we're there, since sensor faults sometimes mask a second problem Same-day service is our standard across Mesa, Gilbert, Chandler, Queen Creek, Scottsdale, Tempe, Phoenix and the rest of the Valley. The service that fixes this When you want it handled rather than diagnosed, this is the page for it: [garage door opener repair](https://farnsworthgarage.com/garage-door-repair-service-installation/garage-door-motor-opener-repair-replacement-installation/). ## What sensor work usually costs This is one of the less expensive things that can go wrong with a garage door, which is worth knowing before you worry. What moves the number: - **Alignment versus replacement** Re-aiming and cleaning is quick. Replacing a failed pair means parts as well as labour. - **Whether the wiring needs work** A splice on an accessible run is fast. A chewed wire inside a finished wall takes longer. - **Whether the brackets survived** Bent or snapped brackets get replaced alongside the sensors, but they're inexpensive. - **Whether the fault is actually in the opener** If the signal is failing at the logic board rather than the sensor, that's a different and more significant repair. - **The age of the opener** On a unit past fifteen years with a board problem, we'll give you an honest view on whether repair or replacement is the better spend. Sensors, brackets and wiring are all small parts, so most of what a [garage door opener repair](https://farnsworthgarage.com/garage-door-repair-service-installation/garage-door-motor-opener-repair-replacement-installation/) costs here is finding which one is lying to you. You'll get a written quote before any work starts. If you're due anyway, our full tune-up is $39.99 and it's the same price in every city we serve. ## Still stuck? We’ll come take a look. Same-day service is our standard across Mesa, Gilbert, Chandler, Queen Creek, Scottsdale, Phoenix, and the rest of the Valley. [Call (602) 935-9766](tel:+16029359766) [Book an appointment](https://farnsworthgarage.com/book-appointment-now/) Due for a check-up while we’re out? Our full tune-up is **$39.99** — same price in every city we serve. ## Related problems we see with this one [Garage Door Won’t Close Read the fix →](https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-wont-close/) [Garage Door Keeps Going Back Up Read the fix →](https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-keeps-going-back-up/) [Garage Door Won’t Open Read the fix →](https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-wont-open/) [Garage Door Opener Beeping Read the fix →](https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-opener-beeping/) ## Look up your exact opener Diagnostic codes, programming steps, and learn-button colors all change by brand and by model. We keep a page for every opener we service — pick your brand below, find your model in the list, and its page has the diagnostic codes, the programming guide, and the manufacturer’s manual. Your model number is on a sticker on the side or back of the motor housing, and it’s usually printed on the inside of the light cover too. [LiftMaster Find your model →](https://farnsworthgarage.com/garage-door-opener-options/liftmaster/) [Chamberlain Find your model →](https://farnsworthgarage.com/garage-door-opener-options/chamberlain/) [Genie Find your model →](https://farnsworthgarage.com/garage-door-opener-options/genie/) [Marantec Find your model →](https://farnsworthgarage.com/garage-door-opener-options/marantec/) [Sommer Find your model →](https://farnsworthgarage.com/garage-door-opener-options/sommer/) [Linear / Nice Find your model →](https://farnsworthgarage.com/garage-door-opener-options/linear/) **Straight to a model page:** [LiftMaster 2420L](https://farnsworthgarage.com/garage-door-opener-options/liftmaster/2420l/) · [Chamberlain B4603T](https://farnsworthgarage.com/garage-door-opener-options/chamberlain/b4603t/) · [Genie 7155D](https://farnsworthgarage.com/garage-door-opener-options/genie/7155d/) ## Questions we get asked about this ### Should both garage door sensors be green? Not necessarily — it depends on the brand. On most LiftMaster and Chamberlain units the receiving eye is green and the sending eye is amber or yellow, so two different colors is normal and correct. What matters is that both are lit and both are steady. A blinking light is the problem, not a mismatched color. ### How do I reset my garage door sensors? There isn't a reset for the sensors themselves — they're simple devices reporting a real condition. What people usually mean is realigning them: loosen the bracket, aim each one at its partner until the indicator holds steady, and tighten. If you want to rule out an electronic glitch at the opener, unplug it for about 30 seconds, but if the underlying fault is still there it will come straight back. ### How do you know if a garage door sensor is bad? Swap the two sensors side for side without changing the wiring. If the dead or blinking light follows the sensor to the other side of the garage, that sensor has failed. If the fault stays on the same side, it's the wiring on that side and a new sensor won't help. That one test saves a lot of guessing. ### Can I run my garage door without sensors? No, and please don't try. Since 1993, federal rules (16 CFR Part 1211) have required every residential opener made in the US to have secondary entrapment protection — in practice that means photo eyes, which is what essentially every manufacturer fits, and openers built to the UL 325 standard won't operate normally without them. More to the point, they're what stops the door on a child or a pet. Replacing a failed pair is inexpensive. ### Why is my garage door sensor blinking? A blinking indicator means the sensor has power but can't get a clean look at the beam. Something is in the way, a lens is dirty, the sensors are out of line with each other, or direct sunlight is washing out the receiver. Work through those four in that order — most people find it in the first two. ### Why won't my garage door close in sunlight? Low direct sun shining into the receiving eye floods it with infrared and drowns out the beam it's trying to see. The opener reads that as blocked. It's common here on west-facing garages, especially in winter when the sun sits low. A small shade over the receiving sensor, or swapping the two sensors side for side, usually solves it permanently. ### Do garage door sensors go bad over time? They do, though they last a long time — fifteen to twenty years is normal. Down here the heat and UV are hard on the plastic housings and their seals, so we see failed units and condensation inside lenses somewhat earlier than you might expect. If the lights won't come on and the wiring checks out, the sensor is the answer. ### Can I replace just one garage door sensor? Technically yes, but we'd replace the pair. They're matched to work together, the second one is usually the same age and heading the same way, and the cost difference is small. Mixing an old sensor with a new one — or worse, mixing brands — is a common source of new problems. ### Why are both my garage door sensor lights off? Two dead lights points at the opener rather than the sensors, because both units share a power feed from the logic board. Check that both wires are properly seated at the terminal block first. If they are, and both sensors are still dark, the board output has likely failed — that's worth a call rather than buying parts on a guess. We'll confirm the board before recommending anything, because that's the point of the [garage door opener repair](https://farnsworthgarage.com/garage-door-repair-service-installation/garage-door-motor-opener-repair-replacement-installation/). ### Where this information comes from - UL 325 — the safety standard governing entrapment protection and auto-reverse on residential garage door openers — photo eyes required on new openers sold in the US since 1993 - [DASMA Technical Data Sheet #167 — Residential Sectional Garage Door and Electric Operator Checklist for Home Inspectors and Consumers](https://www.dasma.com/wp-content/uploads/2023/04/TDS167.pdf) — the checklist item asking whether the photo-eye beam sits no higher than six inches above the floor, and the instruction to stop and call a technician on any “no” - [LiftMaster Model 8500WSM owner's manual (part no. 114A5061)](https://www.devancocanada.com/files/manuals/8500W:installation-manual.pdf) — the manufacturer instruction to install the safety reversing sensor so the beam is no higher than 6 inches above the garage floor, and that the device must not be disabled Serving the Valley ## Where we come out We’re a family-run shop based in **Mesa**, and we cover the whole Phoenix metro. Same-day service is our standard — pick your city, or just call [(602) 935-9766](tel:+16029359766) and we’ll find the soonest slot that works. [Phoenix Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/phoenix-arizona-garage-door-repair-and-service/) [Mesa Our home base](https://farnsworthgarage.com/service-areas-garage-door-repair/mesa-arizona-garage-door-repair-and-service/garage-door-opener-repair-mesa-az/) [Gilbert Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/gilbert-arizona-garage-door-repair-and-service/garage-door-opener-repair-in-gilbert-az/) [Chandler Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/chandler-arizona-garage-door-repair-and-service/) [Queen Creek Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/queen-creek-arizona-garage-door-repair-and-service/) [Scottsdale Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/scottsdale-arizona-garage-door-repair-and-service/) [Tempe Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/tempe-arizona-garage-door-repair-and-service/) [San Tan Valley Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/san-tan-valley-arizona-garage-door-repair-and-service/) [Apache Junction Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/apache-junction-arizona-garage-door-repair-and-service/) [Gold Canyon Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/gold-canyon-arizona-garage-door-repair-and-service/) [Fountain Hills Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/fountain-hills-arizona-garage-door-repair-and-service/) [Maricopa Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/maricopa-arizona-garage-door-repair-and-service/) [Guadalupe Garage door repair](https://farnsworthgarage.com/service-areas-garage-door-repair/guadalupe-arizona-garage-door-repair-and-service/) Not sure if you’re in range? Give us a call — if we can’t get to you, we’ll point you to someone who can. Mesa-based · Serving the whole Phoenix Valley ## Want us to just take care of it? If you’ve worked through this and you’d rather have someone who does this every day handle it — that’s us. Tell us what your garage door opener is doing and we’ll come diagnose it properly. [☎ (602) 935-9766 Call or text — we pick up](tel:+16029359766) [Book online Pick your own time slot](https://farnsworthgarage.com/book-appointment-now/) - **Same-day service** is our standard - **Family-owned** right here in Mesa - **Straight answers** — we’ll tell you if it’s not worth fixing - **Written quote** before any work starts Due for a check-up anyway? Our full tune-up is **$39.99** — same price in every city we serve, and we’ll go through the whole system while we’re there. Mesa · Gilbert · Chandler · Queen Creek · Scottsdale · Tempe · Phoenix · San Tan Valley · Apache Junction · Gold Canyon · Fountain Hills · Maricopa · Guadalupe --- Source: https://farnsworthgarage.com/garage-door-opener-troubleshooting/garage-door-sensor-not-working/ · HTML version with images, galleries and booking form. Farnsworth Garage Door Service, Mesa, AZ · (602) 935-9766