A conveyor that will not run stops everything behind it. Because conveyors combine safety, control, drive and mechanical elements, a repeatable structure saves a lot of lost time.
Safety first
Safety devices must never be bypassed, defeated or overridden as part of fault finding. Follow site isolation procedures and prove dead before mechanical or electrical work.
The fault tree (illustrative)
- START — conveyor will not run
- ↓ E-stop pressed / latched? → Yes → reset
- ↓ Safety circuit healthy? → No → find the device (guard, e-stop, relay)
- ↓ Interlocks satisfied? → No → close guards / clear interlock cause
- ↓ PLC in auto and commanding run? → No → check mode, HMI, logic, permissives
- ↓ Sensors feeding permissives healthy? → No → check presence/level/position sensors
- ↓ VFD / drive healthy and not tripped? → No → read drive fault code
- ↓ Motor receiving command and supply? → No → check output, contactor, cabling
- ↓ Mechanical obstruction or belt issue? → Yes → clear jam / inspect belt and drive
- ↓ Capture and document the cause
The checks in more detail
- Emergency stop and safety circuit: the most common cause is a latched e-stop or an open guard, not a fault. Check before anything else.
- PLC and permissives: conveyors often wait on several permissives (upstream/downstream conveyors ready, level sensors, position sensors). Find which one is false.
- Sensors: a single failed presence or position sensor can hold the whole conveyor. See our guide on diagnosing a failed proximity sensor.
- Drive and motor: read any VFD fault code; confirm the run command and reference are present.
- Mechanical: jams, belt tracking, a seized roller, a worn gearbox or an obstruction all stop the conveyor regardless of the electrics.
Key points
- Most "won't run" conveyors are stopped by a safety device or a missing permissive, not a drive failure.
- Work the tree from safety to mechanical — do not skip to the motor.
- Record the cause so recurring stoppages are recognised and fixed at source.