If your elevator keeps shutting down or stranding riders, there is a good chance the door interlocks are behind it. Interlock faults are the single most common reason elevators stop running - and understanding them helps you tell a quick fix from a door system that is wearing out.
Audience: property manager / building owner. Last reviewed: 2026-08-04 · Editorial review · Confidence: high.
Recurring faults can mean you are paying for a pattern a modernization would end. See your building’s exposure in seconds. No signup required to start.
What is happening
Every hoistway door has an interlock - a switch that confirms the door is closed and locked. They are wired in series into the safety circuit, so the elevator will not move unless every landing door confirms locked. This is one of the most important safety features on the elevator. When one interlock fails to confirm - because a contact is worn, a door is out of alignment, or hardware is loose - the safety circuit opens and the elevator stops.
Compliance alerts, contract negotiation tactics, and cost-saving moves. Written by an elevator expert, for the people who deal with elevator companies. Free, unsubscribe anytime.
Most likely causes
- Worn interlock contacts. The electrical contacts inside the interlock wear and stop making reliable connection. A classic recurring-fault cause.
- Door alignment / hardware wear. A door that has sagged or whose rollers and closer are worn does not seat firmly enough to close the interlock consistently.
- Dirt and debris. Buildup in the interlock or the door track prevents a clean close.
- Loose or aging wiring. Connections at the interlock degrade over decades.
Less common causes
- Building settlement changing door frames over many years.
- A specific interlock model that has become obsolete and hard to source.
- Vandalism or impact damage to a specific landing's door.
What you can safely observe
Note whether the fault is at one landing or several, whether a particular door looks or sounds like it is not closing cleanly, and how often the shutdowns happen. If a specific floor's doors visibly sag or stick, that is a useful clue. Do not open or adjust any door, and above all never allow anyone to bypass or jump out an interlock - that defeats the core safety system.
Safety. The one absolute rule: interlocks must never be bypassed to "keep the elevator running." Bypassing a door lock is how the fatal elevator accidents happen. If a mechanic proposes anything that sounds like disabling a lock, stop and question it. Door hardware is qualified-mechanic-only work.
Urgency & safety level
High, because the failure mode is shutdowns and entrapments, and because interlocks are life-safety devices that must not be worked around. The car will not run unsafely - it fails safe - but the reliability and liability impact is real, and interlock integrity is exactly what inspectors check.
When repeated lock faults mean it is time to modernize
Individual interlocks get cleaned or replaced. But if you are chasing interlock faults across multiple landings on an older unit - worn hardware, obsolete interlocks, aging wiring - a door-system modernization (new operators, hangers, interlocks) often ends the recurring callbacks for less than years of patching. Door components are the highest-wear part of the elevator, so this is a common and defensible modernization driver.
Questions to ask your contractor
- Is the fault at one landing or several, and is it worn contacts, alignment, or wiring?
- Are my interlocks a current part or an obsolete one that is hard to source?
- How many door-lock callbacks has this unit had in the last 12 months?
- Would a door-system modernization cost less over a few years than continued interlock repairs?
Related
- Also see: Why does my elevator stop between floors?
- Also see: Why do my elevator doors keep reopening?
- Equipment: Door operators
- Hub: Problems & symptoms
Recommended next step
If door and lock callbacks keep coming back, they may be costing you more than a fix would. Run your service history and contract through our free scanner to see the pattern.
Step-by-step guidance for entrapments, breakdowns, and other elevator emergencies.
Frequently Asked Questions
What is an elevator door interlock?
It is the safety device that proves a hoistway door is both closed and locked before the elevator is allowed to move. Every landing has one, and they are wired in series - if any single interlock does not confirm locked, the elevator will not run. That is by design: it is what keeps the car from moving with a door open.
Are door lock faults dangerous?
The interlock fails safe - a faulty one stops the elevator rather than letting it run with an open door, which is the whole point. The risk is not the car moving unsafely; it is the shutdowns and entrapments that repeated interlock faults cause, and the temptation for an unqualified person to bypass a lock, which is extremely dangerous and must never be done.