The most common and least serious cause is that the trolley, the part that connects the opener to the door, has been disconnected. The manual release cord disengages the trolley so the door can be operated by hand during a power cut. If that cord has been pulled, or the trolley has not re-engaged properly, the motor runs and moves the trolley mechanism, but it is no longer connected to the door. Re-engaging the trolley, usually by pulling the cord toward the door or running the opener until it reconnects, often restores normal operation.
Inside many openers is a plastic drive gear that can wear out or strip its teeth, especially on an older unit or one that has been overworked by a hard-to-move door. When the gear strips, the motor spins but no longer transfers that motion to the chain, belt or screw. You will often hear the motor running smoothly with a grinding or whirring note, but nothing drives the trolley. This is a common opener fault and usually repairable by replacing the gear, though on an old opener it may prompt a wider conversation about replacement.
If the chain has come off its sprocket, the belt has snapped, or the coupling between motor and screw has failed, the motor runs freely but the trolley does not move. The sound here is often a faster, unloaded motor whir. A visual check along the rail may reveal a hanging chain or a broken belt.
Sometimes the opener really is trying to move a door that physically garage door spring replacement cannot move. A broken spring leaves the door far too heavy for the opener to lift, so the motor strains, hums and stalls. A door jammed by a bent track, an off-track roller or an obstruction also refuses to budge. In these cases the motor labours rather than spinning freely, and may trip its overload protection.

A technician listens to the motor, watches the trolley and rail, and tests the door by hand with the opener disengaged. From the sound and behaviour they quickly separate an opener fault, a disengaged trolley, a stripped gear or broken drive, from a door fault like a broken spring or jam. They then repair the specific cause: re-engaging or repairing the trolley, replacing a gear or drive component, or fixing the spring, track or obstruction that is stopping the door.
If re-engaging the trolley does not solve it, or the motor is straining against a door that will not move, a technician can identify whether garage door sources the fault lies in the opener or the door and repair it safely. A straining motor against a broken spring in particular should not be persisted with, as it risks damaging the opener.
Commonly the trolley has disengaged, a drive gear has stripped, or a drive component has broken, so the motor spins without moving the door.
Usually by pulling the manual release cord toward the door or operating the opener until the trolley reconnects. If it will not reconnect, have it checked.
Yes. A broken spring makes the door too heavy to lift, so the motor strains and stalls rather than moving it.
Often yes on a serviceable opener, by replacing the gear. On a very old unit, replacement of the opener may be the better value.
A1 Garage Doors Gold Coast services homes and businesses across the Gold Coast and surrounding suburbs for repairs, replacements and installations. Contact details are below.
A1 Garage Doors Gold Coast
1 Waterford Court, Bundall, QLD 4217 Phone: (07) 5515 0277 Website: https://goldcoastgaragedoorrepair.com.au A running opener that will not move the door is usually one of a handful of faults, and the sound tells you which. A free, fast whir points to a disengaged trolley, a stripped gear or a broken drive, while a straining, stalling motor points to a broken spring or a jammed door. Start with the simple check of re-engaging the trolley, avoid hammering the button against a door that cannot move, and let a technician separate an opener fault from a door fault and fix the right one. 