Garage Door Opener Runs But the Door Doesn't Move?
Your opener whirs away for its full normal cycle, the light comes on, everything sounds healthy — and the door sits there like nothing happened. It's a strange thing to watch, and the good news is that the most common explanation takes about thirty seconds to fix and costs nothing. The connection between the opener and the door has come apart. Usually that's the emergency release cord doing exactly what it's designed to do, and being forgotten afterwards. Less often, something inside the opener has worn through. This page shows you how to tell which within a minute of walking into the garage.
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.
Stop pressing the button if you see or hear any of this
Most of the causes here are harmless. A couple mean you're actively destroying something with each attempt.
- A grinding or crunching noise while the motor runs.
- White, gray, or beige plastic shavings on the floor underneath the opener.
- A burning smell, or the motor housing hot to the touch.
- The motor humming or buzzing without the chain or belt moving at all.
- You heard a loud bang before this started, and the door is now heavy to lift by hand.
The nylon drive gear inside your opener is a wear part, and once it starts shedding, every additional cycle grinds away what's left. A humming motor that isn't turning is overheating its own windings. And if a spring has broken, the opener is fighting a quarter-ton door it was never meant to lift. In all four cases, stopping now keeps the repair smaller than it would otherwise be. If the counterbalance turns out to be the culprit, that's garage door repair on the same visit.
Call (602) 935-9766What to check in the next 10 minutes
Three checks that identify this almost immediately.
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1Look at the trolley on the rail while the motor runs
The trolley is the sliding piece that travels along the rail above your door. If it moves along the rail and the door doesn't follow it, the two have come apart — that's your answer and it's the easy one.
You’ll know it worked when: You've watched the trolley and know whether it's traveling or stationary.
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2Try lifting the door by hand
If the door lifts easily, it's already disconnected from the opener. If it's locked solid, the trolley is still attached and the problem is further back. If it's heavy but movable, you may have a spring problem instead.
You’ll know it worked when: You know whether the door is free, locked, or heavy.
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3Look at the floor under the opener
Plastic shavings — white, gray, or beige, sometimes fine like sawdust — are a near-certain sign the drive gear has stripped. Take a flashlight and actually look; they're easy to miss on a dusty garage floor.
You’ll know it worked when: You've checked the floor directly beneath the opener head.
Is the trolley moving?
This is the whole diagnosis, and it takes one cycle to answer. Stand where you can see the rail above the door, and press the button.
If the motor only hums or buzzes without any sound of movement at all, that's a different fault again — see cause 4.
Which version is yours?
Match what you're seeing and hearing.
Disconnected from the door arm. Free fix, thirty seconds.
Jump to that fix ↓Drive gear stripped. Stop pressing the button.
Jump to that fix ↓Broken chain or belt, or a failed coupler.
Jump to that fix ↓Capacitor failure. The motor is trying and can't start.
Jump to that fix ↓Chain slack or a snapped belt. Often visible at a glance.
Jump to that fix ↓Not this page — that's a heavy door. Spring problem.
Jump to that fix ↓How the opener actually connects to your door
There's a short chain of parts between the motor and your door, and the fault is always in one of them — so it helps to know what they are.
The motor turns a small drive gear, which is a nylon component roughly the size of a golf ball. Nylon is used because it's quiet and self-lubricating, and because it's designed to be the sacrificial part — if something jams, the gear gives way rather than the motor burning out. That's deliberate engineering rather than a design flaw, but it does mean the gear is a consumable.
The drive gear turns a sprocket, which pulls the chain or belt along the rail. That chain or belt drags the trolley — the sliding block on the rail. And the trolley connects to your door through the door arm, that bent metal bar running from the rail down to the top panel of the door.
The red cord hanging from the trolley disconnects that last link. Pull it and the trolley releases the door arm, so you can lift the door by hand during a power cut. The opener then runs perfectly happily with nothing attached, which is exactly what you're watching when the trolley slides past a stationary door.
One important consequence: a door that's hard to lift will chew through the drive gear. If your springs have weakened, the opener is straining every cycle, and the nylon gear is what pays for it. So a stripped gear often isn't the original problem — it's the symptom of a spring problem that's been going on for months.
So: trolley moving means the last link came apart. Trolley not moving means something inside the opener did.
Match the sound and the movement
What you hear narrows this as much as what you see.
| What you’re seeing | Most likely cause | How urgent | Who should fix it |
|---|---|---|---|
| Trolley slides, door stationary | Emergency release pulled, never re-engaged | Fix now — free | You can do this |
| Motor runs, grinding, nothing moves | Drive gear stripped | Stop using it | Call a pro |
| Plastic shavings under the opener | Drive gear stripped — near certain | Stop using it | Call a pro |
| Motor runs smoothly, nothing moves | Broken chain, snapped belt, or failed coupler | This week | Either — call us if unsure |
| Motor hums, no rotation at all | Failed capacitor | Stop using it | Call a pro |
| Chain sags on the rail | Chain slack, or the sprocket has failed | This week | Either — call us if unsure |
| Door lifts easily by hand | Confirms it's disconnected from the opener | Fix now | You can do this |
| Door is heavy to lift by hand | Spring problem — the gear likely failed because of it | Stop using it — call today | Call a pro |
| Burning smell from the opener | Motor windings overheating | Unplug it now | 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.
The trolley is disconnected from the door
Basic checkBy a comfortable margin the most common cause, and the most satisfying to fix. The red cord hanging from the trolley exists so you can disconnect the door and move it by hand during a power cut. People pull it during an outage, get the car out, and then forget entirely. It also gets caught by roof racks, ladders, and tall vehicles — sometimes without anyone noticing at the time. Once released, the opener runs its whole cycle happily with nothing attached.
How you can tell: The trolley visibly slides along the rail while the door sits still, and the door lifts easily by hand.
- Close the door fully by hand first. This genuinely matters — re-latching a partly open door means it can drop as it connects.
- Find the release lever on the trolley, where the red cord attaches.
- Pull the cord toward the door rather than straight down. On most units you'll hear or feel it click back into the ready position.
- Run the opener normally. The trolley will travel along the rail and re-latch onto the door arm automatically, usually with an audible click.
- Cycle the door once completely to confirm it's properly engaged.
- If the trolley passes the connection point without latching, close the door by hand again and repeat — it only latches in the right position.
You’ll know it’s right when: The door moves with the opener again, and you can see the trolley is latched to the door arm.
The drive gear has stripped
High risk — call a technicianThe nylon drive gear is designed to be the part that gives way — it protects the motor by sacrificing itself. On a chain or belt drive it sits inside the opener housing, and when its teeth wear down or shear off, the motor spins freely without turning the sprocket. It's a genuinely common repair, and on an opener past ten years it's arguably a maintenance item rather than a failure.
How you can tell: The motor runs, often with a grinding or crunching sound, and nothing moves. Look on the floor directly under the opener for plastic shavings — white, gray, or beige, sometimes as fine as sawdust. That's close to conclusive.
The chain, belt, or coupler has failed
Hands-on — moderate riskLess common than a stripped gear but it does happen. A chain can jump off its sprocket or break a link; a belt can snap or shred, usually along an edge; and on screw-drive or direct-drive units the coupler joining the motor to the drive shaft can shear. In each case the motor turns, the drive turns, and nothing downstream moves.
How you can tell: The motor runs smoothly with no grinding, and the trolley doesn't move. Look along the rail — a broken chain or belt is usually visible, and a chain that's jumped its sprocket often sags dramatically.
- Unplug the opener before looking closely at anything on the rail.
- Follow the chain or belt along the full length of the rail, looking for a break, a shredded edge, or a section that's come off its sprocket.
- Check the sprocket at the opener end — a chain that's jumped off usually leaves obvious marks.
- On a screw drive, look at the coupler between the motor and the screw shaft for a sheared or spun connection.
- Note what you find before calling — it speeds up the visit considerably.
You’ll know it’s right when: You've identified whether the chain, belt, or coupler is the failure and stopped operating the opener.
The motor's capacitor has failed
High risk — call a technicianThe capacitor gives the motor its starting kick. Without it the motor can't get moving from a standstill — it draws current, hums, and sits there. It's a small component and a routine repair, but it involves a part that stores an electrical charge even after the opener is unplugged.
How you can tell: The motor hums or buzzes distinctly but nothing rotates at all. No chain movement, no trolley movement, no grinding — just an electrical hum. Sometimes it will start if you give the chain a nudge, which is a strong confirmation.
The door is too heavy and the opener has given up
High risk — call a technicianSlightly different from the others, and worth including because people describe it the same way. If a spring has broken or badly fatigued, the opener is asked to lift 150 to 250 pounds it was never designed to handle. Some openers strain and stop. Some run their cycle while the door barely shifts. And some strip their drive gear in the attempt, which is how this cause and cause 2 end up being the same service call.
How you can tell: Close the door, pull the release cord, then lift it manually. A healthy door feels like about ten pounds and stays wherever you stop it. If it's heavy, drops when you let go, or won't stay put, the springs are the real problem. Also look at the shaft above the door — a broken torsion spring shows a clear gap of an inch or two in the coil.
What your opener is telling you, by brand
Chain and belt drives (most brands)
LiftMaster, Chamberlain, Genie, Craftsman and most others use the same basic layout, so the failure points are shared.
| What you observe | Likely part | What to do |
|---|---|---|
| Trolley moves, door doesn't | Door arm disconnected at the trolley | Re-engage — cause 1 |
| Grinding, plastic shavings | Nylon drive gear stripped | Stop and call — cause 2 |
| Chain sagging or off the sprocket | Chain or sprocket failure | Unplug and inspect — cause 3 |
| Belt shredded along an edge | Belt failure, often from misalignment | Needs replacing and the cause found |
| Hum, no movement anywhere | Capacitor | Unplug immediately — cause 4 |
Screw drive & direct drive
Screw drives (some Genie models) and direct drives (Sommer, some Marantec) have a different layout and different failure points.
| What you observe | Likely part | What to do |
|---|---|---|
| Motor runs, screw shaft still | Coupler between motor and shaft has sheared | Service call — cause 3 |
| Screw turns, trolley doesn't travel | Trolley nut worn out on the screw | Service call — a wear part on screw drives |
| Direct drive motor runs on the rail, door still | Door arm disconnected, or the carriage has failed | Check the release first — cause 1 |
| Grinding on a screw drive | Dry or damaged screw shaft, or worn trolley nut | Service call — these need specific lubricant, not general-purpose grease |
What you’ll need if you’re doing this yourself
- A flashlight — for spotting plastic shavings on a dusty floor and inspecting the rail
- A stepladder — for looking at the trolley, chain, and sprocket properly
- Nothing else, for the common fix — re-engaging the trolley needs no tools at all
Things not to do — and why
Every cycle grinds away more of the drive gear. A partly worn gear is a smaller job than one that's completely destroyed and taken the sprocket with it.
The door can drop as the trolley latches onto the arm. Close it fully by hand first, every single time.
You'd be connecting the opener to a door its springs aren't carrying. That's precisely how drive gears get destroyed — you'd be creating the next problem while fixing this one.
A motor that can't start is drawing current and heating its own windings with nowhere for it to go. Minutes matter — unplug it.
Capacitors hold an electrical charge after the unit is unplugged and need discharging safely. It's a cheap repair done properly and a genuinely dangerous one done casually.
If the gear failed because the door got heavy, a new gear goes the same way within months. Fixing the symptom and ignoring the cause is money thrown away.
Screw drives need a specific lubricant. Ordinary grease attracts dust, turns into a grinding paste, and wears the shaft and trolley nut faster than no lubricant at all.
Why drive gears fail early here
We replace more drive gears in the Phoenix area than the national pattern would suggest, and it comes back to two things.
The first is spring life. Heat cycling is hard on steel, and springs here rarely reach the life a mild climate would give them — and DASMA's cycle-life guidance is narrower than it's usually quoted, pointing at doors left standing open rather than at ambient heat, and our own call history matches it — springs here rarely make the ten years you'd plan around elsewhere. When springs weaken, the door gets heavier, and the nylon drive gear is what absorbs that extra load every single cycle. So our gear failures are frequently downstream of a spring problem the homeowner hasn't noticed yet — which is exactly why we check door balance on every one of these calls rather than just fitting a gear.
- Heavy doors chew gears — weakened springs mean every cycle strains the nylon gear. Most of our gear failures trace back to this.
- Heat softens nylon — the gear sits inside a housing near the ceiling of a garage that passes 130°F. Nylon is more prone to deforming and wearing at those temperatures.
- Grease dries out — the factory grease on the gear and sprocket degrades faster in sustained heat, so the gear runs drier than intended.
- Monsoon dust — fine silt works into the chain and sprocket, increasing friction and passing more load back to the gear.
- The release gets pulled more — storm-season outages mean more people pulling the emergency cord, and more of them forgetting to re-engage it. A good share of these calls are simply that.
Making the drive last
Most of what kills a drive gear is preventable, and it's mostly about not making the opener work harder than it should.
- Do the balance test twice a year — release the door, lift by hand, check it stays where you stop it. A door that's getting heavy is a gear failure in slow motion.
- Lubricate rollers, hinges and the spring annually with a silicone or lithium garage-door product. Less friction means less load on the drive.
- Re-engage the trolley promptly after any outage — and check it latched properly by cycling the door once.
- Listen for changes in the sound — a gear that's starting to wear often gets noticeably noisier before it fails outright.
- Keep the chain at proper tension — a sagging chain slaps and jumps; an overtight one loads the sprocket and bearings. We set this as part of a tune-up.
- Don't ignore a door that's slowed down — a door taking longer to open than it used to is telling you the drive is working harder.
How this usually develops
A stripped drive gear is rarely the first thing that went wrong.
This is the clearest example on the site of why we look at the whole system. Fitting a drive gear to a door with tired springs means we'd be back within months — so we'd rather find that on the first visit and tell you.
When to call us
If the trolley moves and the door doesn't, try re-engaging it yourself first — it's free and it's usually the answer. Call us if you find plastic shavings, hear grinding, hear a hum with no movement, see a broken chain or belt, or if the door is heavy when you lift it by hand.
- Identify in the first few minutes which link in the drive has failed
- Check the trolley, door arm, chain or belt, sprocket, and drive gear
- Release the door and check its balance by hand — the step that finds why the gear failed
- Replace the drive gear, chain, belt, or coupler as needed, with the correct part for your model
- Set chain or belt tension properly rather than approximately
- Inspect springs, cables and rollers, since those are usually the underlying cause
- Run the UL 325 safety reversal test once it's running again and show you the result
- Give you an honest view on repair versus replacement if the opener is old enough for that question
Same-day service is our standard across Mesa, Gilbert, Chandler, Queen Creek, Scottsdale, Tempe, Phoenix and the rest of the Valley.
When you want it handled rather than diagnosed, this is the page for it: garage door opener repair. Depending on what you find, garage door repair may be the closer fit.
What this costs to repair
This spans from free to a significant repair depending on which link failed. What determines it:
- Whether it's just the trolley Re-engaging costs nothing and you can do it yourself. Genuinely the most common outcome.
- Drive gear versus whole assembly A gear kit is a modest part. If the sprocket has been chewed too, that's more.
- Chain versus belt Different parts and different labour. Belt drives are generally more to replace.
- Whether the springs are the real cause If the gear went because the door is heavy, you're looking at spring work as well — and doing only one is a false economy.
- Whether the motor survived A motor that's been running against a jam or humming for a while may have damage of its own.
- The age of the opener Past fifteen years with a failed gear and a failing motor, replacement is often the better spend and we'll say so.
A stripped gear is one of the more predictable garage door opener repair jobs, and it's usually the cheapest outcome on this page. You'll get a written quote before any work starts, and we'll tell you plainly if the honest answer is that repairing isn't worth it. If you're due anyway, our full tune-up is $39.99 — 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.
Due for a check-up while we’re out? Our full tune-up is $39.99 — same price in every city we serve.
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.
Straight to a model page: LiftMaster 83650-267 · Chamberlain C2202T · Genie 3022
Questions we get asked about this
Almost always because the trolley has been disconnected from the door — someone pulled the red emergency release during a power cut and it was never re-engaged. Watch the rail while the motor runs: if the trolley slides but the door stays put, that's it, and re-engaging takes about thirty seconds. If the trolley doesn't move either, something inside the opener has failed instead.
Close the door fully by hand first — this matters, because re-latching a partly open door means it can drop. Then pull the red cord toward the door rather than straight down, which resets the release lever; you'll usually hear it click. Run the opener normally and the trolley will travel along and re-latch onto the door arm with another click. Cycle it once to confirm.
That's the nylon drive gear shedding, and it's close to a definitive diagnosis. The gear is designed to be the sacrificial part that gives way rather than letting the motor burn out. Stop operating the opener — every cycle grinds away more of what's left and can take the sprocket with it, which turns a modest repair into a larger one. Stop at the first grind and the garage door opener repair stays modest.
A distinct hum with no rotation at all usually means the capacitor has failed — that's the component giving the motor its starting kick. Unplug the opener now, because a motor that can't start is heating its own windings with nowhere for that heat to go. It's a small and inexpensive repair, but capacitors hold a charge after unplugging, so it isn't a home job.
Some people do, and gear kits are sold for it. But there are two reasons we'd suggest otherwise. It's awkward overhead work with the opener partly dismantled. More importantly, a stripped gear is usually caused by a door that's gotten heavy — so unless the spring situation gets sorted at the same time, the new gear goes the same way in a few months.
Watch the trolley while the motor runs. Trolley sliding along the rail with the door stationary means it's disconnected — free fix. Trolley not moving at all means the failure is inside the opener, and if you also hear grinding or find plastic shavings on the floor, that's the drive gear.
Usually because the door got heavy. Your springs carry nearly all the door's weight and the opener only adds a nudge — but as a spring fatigues, more of that weight transfers to the drive, and the nylon gear is what absorbs it. Heat is hard on springs here, which is part of why we see this more than the national average. Worth checking door balance rather than just fitting a gear.
It won't damage anything to run it — the opener is just cycling with nothing attached. But you've got a door that's only held by its springs, which means it can be opened by hand by anyone outside if the manual lock isn't engaged. Worth re-engaging promptly for security reasons if nothing else.
On a well-balanced door, often ten to fifteen years — it's genuinely a wear part rather than a failure. On a door with tired springs it can be a fraction of that, because every cycle loads the gear far beyond what it was designed for. That's why gear life is really a question about your springs.
Where this information comes from
- DASMA Technical Data Sheet #190 — Factors Affecting Spring Cycle Life — extreme heat and spring life — the usual root cause of drive gear failure here
- DASMA Technical Data Sheets (full index) — industry standards for door and opener systems
- UL 325 — safety standard for residential garage door openers — the standard behind the safety reversal test
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 and we’ll find the soonest slot that works.
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.
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.
- 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