Summary

"The garage door won't open" covers a wide range of possible faults, and the single most useful triage question is: does the door respond to ANY control method, including the wired wall switch and manually operating the motor unit directly? If a handset doesn't work but the wired wall switch does, the fault is in the remote system, not the opener itself — see the companion remote fault-finding guide. If nothing works — wall switch, handset, nor the motor's own manual trigger — the fault sits in the motor unit, its power supply, or a safety device, and that's what this guide covers.

Domestic garage door openers in the UK are covered by BS EN 13241 (also the relevant standard for the door's own installation — see garage door installation pricing guide), which mandates force limiters and obstacle detection (typically a photocell safety beam across the door opening) on all powered doors. This matters for fault-finding because a door that stops partway, reverses unexpectedly, or won't complete its travel is very often a safety device doing exactly what it's designed to do — a blocked photocell beam, a misaligned sensor, or genuine resistance tripping the force limiter — rather than a motor fault, and misdiagnosing this as "the motor's broken" leads to unnecessary parts replacement.

Key Facts

Quick Reference Table

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Symptom Likely Cause First Check
Nothing happens at all — no motor sound, no movement, from any control method No power to the unit Isolator/fused spur, consumer unit MCB/RCD
Motor hums/runs but door doesn't move Disengaged manual release, or snapped belt/chain/stripped screw-drive Check manual release carriage is engaged; inspect drive mechanism
Door starts to close then reverses/stops partway Photocell safety beam blocked or misaligned Check beam alignment and clean both lenses
Door stops partway during opening or closing, every time, same position Force limiter tripping on a mechanical obstruction/binding Check track alignment, rollers, and door balance at that position
Motor strains, labours, or trips overload attempting to lift the door Spring balance fault (door too heavy for the motor to lift correctly) Check door's own spring balance/counterweight, independent of the opener
Works sometimes, fails intermittently with no clear pattern Marginal power supply, loose connection, or a sensor on the edge of alignment Check supply voltage and all terminal connections; recheck beam alignment precisely
Battery backup unit "dead" during a power cut Depleted/failed backup battery, or it's just a genuine mains outage Confirm mains status separately; test/replace backup battery

Detailed Guidance

Step 1: confirm this is a motor/opener fault, not a remote fault

Before working through this guide, confirm the wired wall switch (if fitted) and the motor unit's own manual trigger button (usually on the unit itself) also fail to operate the door. If the wall switch works but a handset doesn't, the fault is in the remote receiver/handset system specifically — see garage door remote not working, which covers that fault path in full.

Step 2: power first

Check the dedicated isolator or fused spur feeding the opener is switched on, and check for a tripped MCB or RCD at the consumer unit. If the unit includes a battery backup (common on newer models to allow operation during a power cut), confirm whether the complaint is actually "no mains power" with a depleted or failed backup battery masking the real cause — test or temporarily bypass the battery question by confirming mains supply status independently.

Step 3: manual release and drive engagement

Every powered garage door has a manual release (commonly a red pull cord or a lever) that disconnects the door from the motor's drive carriage, allowing hand operation during a power cut or fault. If this has been pulled — sometimes during a previous power cut and never reset, or pulled by someone trying to force a stuck door — the motor can run perfectly normally while the door itself stays disconnected from the drive, which looks confusingly like "the opener's dead" rather than "the opener's running but not connected." Re-engage the carriage per the manufacturer's instructions (usually operating the door manually to the fully closed or fully open position first, to realign the carriage correctly) before further diagnosis.

Step 4: safety beam (photocell) check

GARAGE DOOR OPENER NOT WORKING — DECISION TREE
(assumes wall switch AND handset both fail — confirmed opener-side fault)
|
├─ Check power: isolator on, no tripped MCB/RCD, backup
│  battery (if fitted) not masking a genuine mains fault
│   └─ No power confirmed → restore power, retest
│
├─ Check manual release/drive carriage is engaged, not
│  disconnected from a previous manual operation
│   └─ Disconnected → re-engage per manufacturer instructions,
│       retest
│
├─ Operate the control — does the motor run (audible hum/
│  movement sound) even though the door doesn't move?
│   ├─ YES, motor runs, door doesn't move →
│   │   drive mechanism fault (belt/chain/screw-drive) →
│   │   inspect and repair/replace drive component
│   │
│   └─ NO, nothing happens at all, motor silent →
│         │
│         ├─ Check safety beam (photocell) alignment and
│         │   lens cleanliness at both transmitter and
│         │   receiver — many units refuse to operate AT ALL
│         │   (not just refuse to close) if the beam reports
│         │   a persistent fault
│         │   └─ Beam blocked/misaligned/dirty → clear
│         │       obstruction, realign, clean, retest
│         │
│         └─ Beam confirmed working correctly →
│             suspect control board or motor fault →
│             further electrical diagnosis needed
│
└─ Door moves partway then stops/reverses at the SAME
    position every time → force limiter responding to a
    genuine mechanical obstruction or binding at that point
    → inspect door track alignment, rollers, and spring
    balance (NOT primarily an opener fault)

Spring balance — a door fault that looks like an opener fault

If the opener's motor, drive, power supply, and safety sensors all check out sound, but the motor audibly strains or trips its overload protection specifically when lifting the door (rather than lowering it), suspect the door's own spring balance system rather than the opener. A door that's correctly balanced should feel close to weightless when lifted by hand with the opener disconnected (via the manual release) — a door that feels heavy or unbalanced by hand confirms the spring system, not the motor, needs attention. Torsion and extension spring adjustment/replacement on garage doors carries genuine risk of injury from stored spring energy and should only be carried out by someone competent and equipped for it.

Frequently Asked Questions

The door opens fine but won't close — is this the same fault?

Often not a motor fault at all — check the safety beam (photocell) first, since many openers are specifically designed to refuse to close (while still allowing opening) if the safety beam is blocked, to prevent closing onto an obstruction. This is the single most common cause of "opens but won't close."

Can I just disable the safety sensor to get the door working while I wait for a repair?

No — do not bypass or disable a safety photocell or force limiter. These exist specifically to prevent crushing and trapping injuries under BS EN 13241's safety requirements, and a door operating with a disabled safety device is a genuine hazard, particularly in a household with children or pets. Fix the underlying cause (obstruction, misalignment, dirty lens) rather than removing the safety device.

The motor runs but the door doesn't move at all — what's wrong?

Check the manual release/drive carriage is properly engaged first — this is the fastest and most common cause of this exact symptom. If the carriage is correctly engaged and the motor still runs without moving the door, suspect a snapped drive belt or chain, or (on screw-drive units) a stripped drive screw thread.

Is it worth repairing an old opener or should it be replaced?

This depends on the specific fault and the unit's age — a safety beam, drive belt, or manual release issue is usually a straightforward and worthwhile repair on almost any unit. A genuine control board or motor winding failure on an older unit is more often economically comparable to, or more expensive than, replacing the whole opener with a current model that also brings updated safety features — price both options for the customer rather than defaulting to either.

Regulations & Standards