A controller records events in the order they arrive, and the first event is usually the cause while the last is the shutdown. Reading the list backwards – last fault first – is why the same unit gets visited three times.
Reading the list in the right direction
| Position | What it usually is |
|---|---|
| First event in the burst | The cause: a contact opened, a feedback pulse was lost, a phase dipped |
| Middle events | Consequences: the drive ramped down, levelling failed, doors held |
| Last event | The protective shutdown – the code that gets reported by the passenger |
Context that turns a code into a diagnosis
- Where was the car? A fault at one landing is a landing problem; a fault at a point in time is a load or temperature problem.
- What was it doing? Starting, accelerating, at speed, decelerating, levelling, doors open with a call held.
- What was the load? Full, empty, or a specific imbalance – many faults only appear at one end of the load range.
- What happened just before? Power event, cleaning, building works, a passenger holding the door, another trade in the machine space.
- Is it repeating? The same fault at the same position is a physical defect; random occurrences point at supply, communication or an intermittent contact.
Translate the code into a subsystem
Most code families map to a subsystem, and that is enough to start:
- Door / gate circuit – a proving contact opened while running.
- Safety chain – pit, governor, or a device operated.
- Feedback / position – encoder, tape, coupling, or a count that no longer matches the building.
- Drive – overcurrent, DC bus, thermal, or a torque limit reached.
- Supply – phase loss, low voltage, phase rotation.
- Communication – a node or loop dropped out; the fault is reported wherever the controller sits, not where the problem is.
Do not clear the list before recording it. Photograph or transcribe the full list with timestamps, and write down the car position and load. Clearing first destroys the only evidence of the cause, and the unit will return with the same fault.
Related: control systems, drives and motors, forum threads on fault codes.