How a passenger lift works

The main components

A traction lift has a car and a counterweight suspended by steel ropes or belts that pass over a sheave driven by the machine. The counterweight balances the car plus roughly half the rated load, so the motor only has to move the difference. This is the drive arrangement in most modern commercial passenger lifts and in the majority of block-of-flats installations.

Fixed to the shaft are the guide rails that keep the car and counterweight travelling true. At the bottom of the shaft sit the buffers — energy absorbers of last resort if the car ever overtravels. Wear or contamination on any of these components tends to surface as one of the symptoms covered in the troubleshooting index long before it becomes a safety event.

What happens when you press a button

A landing call registers with the controller, which selects a car using its dispatch algorithm and books the stop into that car's queue. If a lift ever stops responding at the landing button, that is the out-of-service pattern — the controller has either dropped the call or taken the car out of service on a fault.

The car levels at the floor, the door operator opens the car doors, and the landing doors follow because they are mechanically coupled via a clutch on the car door. Two common faults from this stage — the lift stopping short of the landing sill and the doors reopening every time they try to close — are documented in levelling problems and doors that keep reopening.

Traction and hydraulic lifts compared

Hydraulic lifts take a completely different approach: instead of hanging the car from ropes over a driven sheave, a pump pushes oil into a ram that lifts the car from below, and the car descends by letting that oil back out through a control valve under gravity. There is no counterweight, the machinery lives in a small plant space rather than a motor room at the top of the shaft, and the structural loads land on the pit rather than on the building's head. That makes hydraulics common in low-rise buildings, in retrofits into existing structures, and in goods lifts where load capacity matters more than travel speed or energy efficiency.

The practical difference for an owner shows up in the symptoms. Hydraulic installations drift down slowly from a landing when a valve or seal passes, run smoother going up than coming down, and become noticeably slower or more erratic as the oil temperature changes through the day. Traction installations are far more sensitive to rope, sheave and brake condition, and their faults tend to announce themselves as vibration, unusual noise or repeated levelling errors rather than gradual sinking. Knowing which arrangement you have is often the first thing a service desk will ask, and it is usually written on the plate at the landing or in the maintenance log.

Machine-room-less traction lifts sit between the two in owner terms. They occupy no separate plant room, which is why they were specified, but every component that would once have been reachable from a motor room is now inside the shaft — so access for diagnosis and for parts replacement takes longer, and a fault that would have been a short visit on an older installation can involve more preparation. None of that changes what you should do at the landing, but it does explain why two lifts with identical symptoms can attract very different repair timescales.

Turning observation into a useful fault report

Knowing the components is only useful if it changes what you say when you report a problem. A service desk decides which engineer to send, which parts to load and how quickly to attend from the description it is given, so "the lift is broken" reliably produces a diagnostic visit followed by a second visit with the right component. Describing the equipment, the behaviour and the history in three short lines frequently collapses those two visits into one.

The equipment line is the plate at the landing: lift type, manufacturer, model, any unit or job number, and roughly how old the installation is. The behaviour line is what the lift is doing right now, in the present tense — car position and whether it is level, door state, what any display or indicator shows, whether call buttons illuminate and stay illuminated, and any repeating sound. The history line is when it started, whether it is constant or intermittent, whether it is worse in one direction or at one floor, and what changed beforehand: a power cut, water ingress, building works, a propped door or a recent engineer visit.

Add three facts that are routinely omitted and often change the priority: whether anyone is inside, whether the lift has been taken out of service and signed, and who holds the maintenance contract. In a building with a group of lifts, say how many cars are affected — one car points at that car, all of them point at the group controller or the supply.

What an owner can safely observe

Almost everything useful about a lift fault is visible from the landing without opening anything. Note where the car is stopped and whether it is level with a floor; whether the doors are fully open, fully closed or held part-open; what the position indicator and any display are showing, including codes, symbols or a blank screen; whether the landing call button illuminates and stays illuminated; and any sound that repeats — a relay clicking, a motor humming without movement, a beeper, or a grinding or scraping as the car moves.

Timing matters as much as the symptom. Record when the behaviour started, whether it is constant or intermittent, whether it is worse at particular floors or in one direction of travel, and whether anything changed beforehand: a power cut, water ingress, building works, a delivery that propped the doors, or a recent engineer visit. Where a building has a group of lifts, note whether one car or all of them are affected — that single observation often decides whether the problem is in a car, in the group controller or in the supply.

Nothing in this entry asks you to go further than that. Do not force doors, attempt to move a stuck car, remove a panel, or enter a pit or shaft: the components described above store energy, move without warning under test conditions, and are protected by interlocks that exist precisely because untrained access is dangerous. Take the lift out of service, sign every landing it serves, and report the observations you have gathered.