ApprenticeMedium risk

Limit switch stuck made (won't release)

A mechanical limit switch stays operated even after the actuator leaves it — the input stays made, so the machine thinks it's still at that limit.

Start fault-finding

Safety first

A stuck limit can mask a real end-of-travel and allow overtravel if bypassed. Don't defeat it. Confirm true position before any movement.

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.

Full detail — causes, the why, and common mistakes.

Likely causes

Ranked from most to least likely.

1
Mechanical lever/plunger jammed
Most likely
Dirt, corrosion, or damage stops the lever or plunger returning, holding the contacts operated.
2
Welded/stuck internal contact
#2
The switch contact has welded or stuck closed and won't open.
3
Actuator/cam holding it operated
#3
A mis-set cam or actuator keeps the switch pressed when it shouldn't.
4
Wiring short making the input look 'made'
Least likely
A short in the wiring holds the input active independent of the switch.

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.

Test 1 of 3

With the actuator clear, watch whether the switch mechanically returns to rest.

Expected reading

Lever/plunger returns freely; contacts release.

Your actual reading

If it passes

Mechanically returns — check the contact and wiring.

If it fails

Lever/plunger jammed — clean/free or replace the switch.

Often leads toLimit switch or proximity sensor not being detected Travel limit stops a direction too early

View all expected readings at once

1. With the actuator clear, watch whether the switch mechanically returns to rest.

Lever/plunger returns freely; contacts release.

2. Isolate and check across the switch contact at rest (should be open for an NO held by actuator).

Contact opens when the switch is at rest.

3. Confirm the cam/actuator isn't holding it, and check the wiring isn't shorting the input active.

Cam/actuator clear at rest; no wiring short.

Fault-finding flowchart

The same logic as a decision tree.

1
start
Limit stuck made
→ step 2
2
decision
Does the switch mechanically return to rest when clear?
Yes→ step 3No→ step 4
3
decision
Does the contact open at rest?
Yes→ step 5No→ step 6
4
result
Jammed lever/plunger — free or replace the switch.
5
decision
Is the cam/actuator clear and the wiring un-shorted?
Yes→ step 7No→ step 8
6
result
Stuck/welded contact — replace the switch.
7
result
Re-verify the input reads correctly now.
8
result
Mis-set cam or wiring short — correct it.

Common mistakes apprentices make

Bypassing the stuck limit to keep running and risking overtravel.
Assuming a wiring fault when the lever is simply jammed.
Not checking the cam/actuator setting.
Replacing the switch without finding a wiring short.

When to stop & escalate

Limit switches on overtravel/safety duties are critical — confirm the real position and the safe limits before any movement, and replace (don't bodge) a faulty switch.

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.

Related faults

Limit switches & sensors

Limit switch or proximity sensor not being detected

A limit switch or proximity/photo sensor isn't registering — the machine doesn't stop at position, the input never makes, or the sensor LED looks wrong for the target's position.

5 causes4 test steps

ApprenticeMedium risk

Forward / reverse circuits