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Limit switch not stopping movement (overtravel)

A travel/limit switch that's supposed to stop a movement isn't stopping it — the machine drives past the limit (overtravels), or only stops on the backup/hard stop. A potentially dangerous fault.

Start fault-finding Log readings Enter Job Mode

Safety first

A limit that fails to stop a movement is a safety fault — keep clear of the travel path and treat the machine as able to overrun. Isolate and secure movement before working on the switch, and never defeat a limit to keep production going.

Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.

Apprentice mode

Full walk-through — the why, what readings mean, mistakes & safety.

Likely causes

Ranked from most to least likely.

1
Switch contact welded/stuck or wrong contact used
Most likely
If the stop relies on a contact that's welded closed, or the circuit was wired through the wrong (normally-open instead of normally-closed) contact, the stop command never opens.
2
Actuator/lever not being struck
#2
A bent, broken, or misadjusted lever/roller means the cam or dog passes without operating the switch, so it never signals the limit.
3
Limit not wired to actually stop the drive
#3
The limit input reaches the PLC/drive but the logic doesn't act on it (programming/parameter error), so the movement isn't commanded to stop.
4
Bypassed or jumpered limit
Least likely
A limit previously strapped out for commissioning and never restored leaves the stop function defeated.

Reports are saved on this device to reflect what you actually find.

Testing sequence

Work through one test at a time. Expected reading and what each result means.

On the tools? Job Mode shows one test at a time with thumb-sized buttons — your place and readings carry straight over.

Enter Job Mode

Test 1 of 3

With movement isolated/secured, operate the switch by hand and confirm its contact changes state (and that the circuit uses the correct fail-safe contact).

Expected reading

Contact changes state cleanly; stop uses a normally-closed (fail-safe) contact.

Your actual reading

If it passes

Switch operates correctly — check the actuation and the control logic.

If it fails

A welded/stuck contact, or the wrong contact used, means it can't signal a stop — replace the switch / correct the wiring to fail-safe.

Often leads toTravel limit stops a direction too early Limit switch stuck made (won't release)

Mark this test

View all expected readings at once

1. With movement isolated/secured, operate the switch by hand and confirm its contact changes state (and that the circuit uses the correct fail-safe contact).

Contact changes state cleanly; stop uses a normally-closed (fail-safe) contact.

2. Inspect the lever/roller/actuator and the cam/dog alignment; confirm the switch is physically struck at the limit.

Actuator is struck firmly and squarely at the limit position.

3. Confirm the limit input is seen by the controller AND that the logic/parameters actually stop the movement; check nothing is jumpered out.

Controller sees the input and stops the drive; no bypass present.

Fault-finding flowchart

The same logic as a decision tree.

1
start
Limit switch not stopping movement
→ step 2
2
decision
Does the contact change state, using a fail-safe (NC) contact?
Yes→ step 3No→ step 4
3
decision
Is the actuator actually struck at the limit?
Yes→ step 5No→ step 6
4
result
Welded/stuck or wrong contact — replace switch / rewire to fail-safe NC.
5
decision
Does the controller act on the input (no bypass)?
Yes→ step 7No→ step 8
6
result
Lever/roller bent or misadjusted — repair/realign.
7
result
Recheck the full stop chain end-to-end; ensure safety functions use rated devices.
8
result
Logic doesn't stop the drive, or a jumper is in place — fix logic/parameter or remove bypass.

Common mistakes apprentices make

Wiring the stop through a normally-open contact so a broken wire/failed switch doesn't fail safe.
Leaving a commissioning jumper across the limit.
Assuming the switch works because it 'clicks' without confirming the contact and the logic.
Relying on the limit when it feeds a safety function that should be a rated safety device.

When to stop & escalate

A movement that overtravels is a safety hazard — stop using it and escalate immediately. If the limit forms part of a safety function, it must be a suitable rated device and correctly applied; flag any defeated or non-fail-safe arrangement for proper rectification. Never run the machine with the limit bypassed.

If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.

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