Garage door problems
Operator running but door not moving
If a UK garage door operator runs but the door doesn't move, the trolley is usually disengaged from the manual release cord, or the operator's drive gear has stripped internally. Both are common after a power cut or a forced manual opening. A stripped gear needs a new operator, typically £180–£500 inc. VAT and fitting.
Check the manual release first
Almost every UK electric operator has a manual release — usually a red pull cord hanging from the trolley on the ceiling rail — that disconnects the door from the motor so it can be opened by hand, for example during a power cut. If this has been pulled and not reset, the operator will run its full cycle sound and all, but the trolley just travels along the rail without the door attached. Look for the cord hanging down and check whether the trolley carriage is sitting where it should be.
A stripped internal gear
Inside most chain and belt operators is a plastic drive gear that transfers motor torque to the chain or belt. This gear is deliberately the weakest part of the drivetrain — it's designed to strip under excess load rather than let the motor burn out or the door be damaged. A door that has been struggling (icy tracks, a failing spring) for some time is a common lead-up to this failure. A stripped gear means the motor spins freely with no load, which is why it sounds normal but nothing happens.
Belt or chain has come off or snapped
On belt and chain-drive operators, a belt that has jumped its sprocket or a chain that has snapped will produce the same symptom — the motor runs, but there's no mechanical connection to the trolley.
A hidden spring failure
Occasionally the real cause is a broken spring: the operator tries to lift the door, meets far more resistance than expected, and its built-in force-limit safety under BS EN 12453 stops the motor almost immediately, which can sound like the operator running without moving the door.
| Cause | DIY fixable | Typical cost |
|---|---|---|
| Trolley disengaged from release cord | Yes | £0 |
| Stripped internal drive gear | No | £180–£500 (operator repair/replacement) |
| Snapped chain or belt | No | £180–£500 |
| Underlying broken spring | No | £150–£350 |
Prices include VAT. A call-out fee of £40–£80 may apply on top.
Step by step
1.Check the release cord and trolley
Look along the ceiling rail for the trolley carriage and the release cord. If the cord is hanging loose and the trolley has separated, re-engage it by pulling the cord towards the operator (following your manual’s exact procedure) and manually sliding the door until it reconnects.2.Listen for the pattern
A smooth continuous hum with no strain suggests a stripped gear or disconnected drive. A strained, grinding sound followed by a sudden stop suggests the operator has hit its force limit — possibly a spring problem underneath.Safety: If you suspect a broken spring is the underlying cause, stop testing the operator and do not attempt any spring work yourself — book an engineer.
3.Inspect the chain or belt
With the power off, visually check the drive chain or belt for a snapped link, a jumped sprocket, or visible slack.4.Book an engineer for internal drive faults
A stripped gear or failed drivetrain is a workshop or on-site parts job. Note the operator’s brand and model if visible — it speeds up sourcing the right part.
Questions people ask
- Why does my garage door operator make noise but the door doesn’t open?
- The most common UK cause is the trolley being disengaged from the release cord, often after a power cut prompted a manual opening that was never reset. The second most common cause is a stripped internal drive gear, which needs a repair or new operator.
- Can I fix a stripped garage door operator gear myself?
- It is a specialist repair involving stripping the operator casing and replacing an internal part — most UK engineers price it as a like-for-like repair or replacement rather than a DIY job, typically £180–£500 inc. VAT.
- How do I re-engage the manual release cord?
- Pull the release cord towards the operator (not down) following your specific manual’s instructions, then push the door by hand until the trolley clicks back into the drive carriage. Procedures vary slightly between operator brands, so check your manual if unsure.
- Could a broken spring be the real cause?
- Yes — if the operator strains hard and cuts out quickly rather than running freely, a broken spring forcing the motor to work against the door’s full weight is a likely underlying cause, and it should be checked before assuming the operator itself has failed.
UK standards and regulations referenced
- BS EN 12453:2017+A1:2021
- BS EN 12635
Related
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