You press the button. The light comes on, the motor spins up, you can hear it working away up there — and the door does not move. Not a shudder, not an inch. Somewhere above your car something is turning enthusiastically and achieving nothing.
The good news is that this particular symptom is unusually honest. A motor that runs but does not move the door has broken the connection between itself and the door, and there are only a handful of places that connection lives. One of them is free to fix.
Start here, because it is free
The trolley is disconnected. That red cord hanging from the rail disengages the door from the opener so you can lift it by hand in a power cut. Pull it and the motor still runs, the light still comes on, and the carriage slides up and down the rail without taking the door with it.
It gets pulled by accident more often than anyone admits: a tall load in a roof box, someone hanging a bag on it, a child who found a dangling rope. It also gets pulled deliberately during a power cut and then forgotten.
To check: look at the rail while someone presses the button. If a plastic carriage is travelling along it and the arm to the door is not attached, that is your answer. Close the door fully, then press the button and let the trolley run until it clicks back on. On most units that is the whole repair.
If that was it, you are done, and this was the cheapest garage door article you will read today.
The stripped gear
If the trolley is connected and the motor still runs uselessly, listen to the sound. A stripped drive gear has a particular character: a fast, light, slightly plasticky whirring, much quicker than the door's normal travel, sometimes with a rhythmic tick.
Inside a chain-drive opener there is a nylon gear that the motor's steel worm drive turns. Nylon against steel is a deliberate choice — the gear is designed to be the part that fails, because a stripped gear is a part and a burnt-out motor is an opener. It is a fuse made of plastic.
They fail two ways. Honestly, at the end of a long life, on an opener old enough to have earned it. Or early, because something has been overloading them. That second case is the one worth caring about, and the usual culprit is a door the springs are no longer holding up. Replace the gear on an unbalanced door and you will meet the same failure again, on a schedule.
So: if the gear went at fifteen years, it went of old age. If it went at four, something else is wrong and the gear is the messenger.
The broken spring
A door with a snapped torsion spring weighs what it actually weighs — anywhere from about 150 pounds to well over 400 — and no residential opener will move that. Many will try. Some will hum, strain, and give up. Some will lift it two inches and set it back down.
Look above the door at the steel shaft. A torsion spring in one piece is a continuous tight coil. A broken one has an obvious gap, usually a couple of inches, sometimes with the ends splayed apart. On doors with two springs, check both.
If you find a gap, stop pressing the button. Every attempt is loading the opener, the cables and the drums with a weight none of them are rated for, and the cables are the part that objects most expensively. Leave it closed and call someone.
The sheared shaft or stripped drum
Less common, and the reason a technician looks up rather than just listening. If the splined shaft has sheared, or a drum has stripped where the cable seats, the springs can be perfectly healthy and the door still will not move, because the torque has nowhere to go. It usually announces itself with slack cable on one side and a door sitting crooked in its opening.
The order to work through it
- Look at the rail. Trolley connected? If not, reconnect — free.
- Look at the springs. Any gap in the coil? If yes, stop and call.
- Pull the red cord and lift the door by hand (door closed first, power off first). If it lifts easily and stays at waist height, the door and springs are fine and your problem is inside the opener. If it is desperately heavy, it is not the opener.
- Listen to the motor. Fast plasticky whirring with the trolley connected and the door light: stripped gear.
That sequence is deliberate. It is ordered cheapest and safest first, and it stops before the two places where a home repair goes badly wrong.
What this costs, in shape rather than numbers
- Reconnecting the trolley: nothing. Do it yourself.
- A gear kit on an otherwise sound opener is one of the smaller repairs in this trade, and on a good unit it is well worth doing.
- A spring is a spring job — see the door's weight, the number of springs, and whether the failure took a cable with it.
- Shaft or drum work is the expensive end, because it is parts plus re-tensioning the whole system.
When the opener is genuinely worth replacing
Not on the strength of one stripped gear. The cases where we say replace it:
- It predates 1993 and has no photo eyes. Those were made mandatory for a reason, and no repair fixes their absence.
- The motor itself has failed, as opposed to the gear.
- Parts have stopped existing. On a genuinely old unit, the logic board is the wall you eventually hit.
- You actively want what the new ones do — a quiet belt drive under a bedroom, a battery backup that keeps working in an outage, a phone app you will use more than twice.
An opener that has run for fifteen years and stripped one plastic gear is not telling you it is finished. It is telling you the fuse worked.
And the disappointing likelihood
Of every call that comes in described exactly this way, a decent share are the red cord. We turn up, close the door, press the button once, and hand it back working. It is a poor business model and an excellent afternoon.
Garage Door Doctor’Z · (833) 991-3899 · doctorzgaragedoor.com
CSLB C61/D28 · Lic. 1138150 · Serving the Sacramento Valley since 2018.
