The gate is definitely closed but the lift says it's open. What's happening?

The interlock sensor is reporting bad on a good gate. Cause is either sensor drift, wiring damage, or debris in the latch. All are engineer-only diagnoses — do not attempt to work on the sensor yourself.

Can I put a magnet on the switch to hold the interlock closed?

No. This is illegal on workplace lifts and unsafe on any lift — the whole purpose of the interlock is defeated. It is also easily detected on the next LOLER inspection and will fail the report.

The gate is stiff to close. Related?

Yes — a stiff gate is often not being closed with enough force to seat the latch. Have the hinges checked at the next service. In the meantime, close the gate deliberately and firmly enough to hear the click.

How often should gate interlocks be tested?

Every LOLER thorough examination (6-monthly on workplace lifts) must include an interlock proof test. On domestic lifts, the annual service includes it. Ask to see the record on the report.

Is a gate interlock the same as a door interlock on a cabin lift?

Functionally yes — both prevent lift movement with an opening not properly closed. Mechanically they differ: cabin-lift interlocks are usually motor-driven and centralised; platform-lift gate interlocks are simpler reed-switch or mechanical hook designs on each landing.

Platform Lift Gate Interlock Fault Guide

Platform lift gate interlock fault: causes and checks

The gate interlock is what stops a platform lift moving with a gate open. When it faults, the lift is stuck — and getting it back into service means understanding whether the gate really is open, or just being reported as open.

How the interlock proves the gate is closed

UK platform lifts use one of two systems on each gate:

Reed switch + magnet. A magnet on the gate, a reed switch on the frame. When the gate closes, the magnet pulls the reed closed and the controller sees the gate as shut.
Mechanical latch with proof. A physical hook that drops into a slot as the gate closes, with a switch that proves the hook is home.

Either way, the interlock is either ‘good’ or ‘bad’ — there is no in-between. A gate that looks closed but reports bad is either genuinely misaligned or the sensor has failed.

Owner checks before calling

Safe to check yourself

Open every gate fully, then close each firmly. Look for the mechanical click of the latch dropping.
Wiggle each gate at the latch — no play should be present.
Look for debris in the latch slot on the frame — grit, dead leaves, wasp nests on outdoor lifts.
On lifts with a visible magnet-and-reed pair, check nothing has been placed against the sensor from the far side (paint, a fridge magnet, a screw driven into the frame during unrelated work).

Reed switch alignment drift

Reed switches drift out of alignment over time, especially on gates that are opened and closed hundreds of times a week. Once the magnet no longer sits directly opposite the switch when the gate is closed, the interlock will fail. This is not user-serviceable — the switch is set with a feeler gauge and any adjustment must be verified by a competent engineer.

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Describe your symptom →

Latch failure — the mechanical version

The physical hook that drops into the frame slot can bend, wear or break. Symptom: the gate closes but doesn't click, and the interlock proves bad. Do not attempt to repair the latch yourself; a bent latch reshaped with pliers will pass proof but fail on load, and the whole gate assembly may need replacement.

Multiple gates failing at once

Stop — call an engineer

If more than one gate reports interlock fault in the same week, do not keep resetting. This pattern almost always means:

Wiring loom damage in the controller cabinet (rodents, water ingress).
Controller board failure.
A recent alteration to the lift (repaint, gate hinge replacement, structural work) has disturbed something.

Isolate the lift and give the engineer the full list of fault times.

The manual key release — for engineers only

Every UK platform lift landing gate has a triangular emergency-key release from the landing side. This is for competent-engineer use to recover a trapped user from a stalled lift. It is not for owners to bypass a nuisance interlock fault; every UK gate incident of the last decade has traced back to a misused key release.

Frequently asked questions

The gate is definitely closed but the lift says it's open. What's happening?: The interlock sensor is reporting bad on a good gate. Cause is either sensor drift, wiring damage, or debris in the latch. All are engineer-only diagnoses — do not attempt to work on the sensor yourself.
Can I put a magnet on the switch to hold the interlock closed?: No. This is illegal on workplace lifts and unsafe on any lift — the whole purpose of the interlock is defeated. It is also easily detected on the next LOLER inspection and will fail the report.
The gate is stiff to close. Related?: Yes — a stiff gate is often not being closed with enough force to seat the latch. Have the hinges checked at the next service. In the meantime, close the gate deliberately and firmly enough to hear the click.
How often should gate interlocks be tested?: Every LOLER thorough examination (6-monthly on workplace lifts) must include an interlock proof test. On domestic lifts, the annual service includes it. Ask to see the record on the report.
Is a gate interlock the same as a door interlock on a cabin lift?: Functionally yes — both prevent lift movement with an opening not properly closed. Mechanically they differ: cabin-lift interlocks are usually motor-driven and centralised; platform-lift gate interlocks are simpler reed-switch or mechanical hook designs on each landing.