Jog / inch function not working
The jog (inch) control doesn't move the motor in short bursts — pressing jog does nothing, or it latches and runs continuously instead of jogging.
Safety first
Jog is often used during setup with guards open — extra caution. The motor moves on each press; keep hands and tools clear of the drivetrain.
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
Jog bypasses the seal-in — wiring fault
Most likelyJog should energise the contactor without the seal-in latch. A wiring fault either blocks it or lets it latch and run on.
- 2
Jog control/relay faulty
#2A dedicated jog relay or its contacts have failed, so the jog path doesn't work.
- 3
Jog button faulty
#3The momentary jog button isn't making (does nothing) or is sticking (runs on).
- 4
Interlock with run mode blocking jog
Least likelyA mode interlock between run and jog is mis-set, blocking jog.
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.
Press jog and observe: nothing at all, or does it latch and run continuously?
Short burst of movement that stops when released.
Jogging correctly — issue may be elsewhere.
Nothing → check button/control path. Runs on → seal-in isn't being bypassed.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Jog not working
→ step 2 - 2decision
When you press jog, does it do nothing or run on continuously?
Yes→ step 3No→ step 4 - 3decision
Is the jog path (button/relay/seal-in bypass) sound?
Yes→ step 5No→ step 6 - 4result
Jogs correctly — look elsewhere.
- 5decision
Is the run/jog mode interlock set to allow jog?
Yes→ step 7No→ step 8 - 6result
Fault in jog button/relay or seal-in bypass — repair it.
- 7result
Re-check the jog wiring.
- 8result
Mode/interlock blocking jog — set correctly.
Common mistakes apprentices make
- Not understanding that jog should bypass the seal-in (so it doesn't latch).
- Missing a sticking jog button that makes it run on.
- Overlooking a run/jog mode interlock.
- Jogging near the drivetrain without keeping clear.
When to stop & escalate
Because jog is often used with guards open, treat any unexpected latching (run-on) as a priority safety fix. Confirm the jog logic against the drawings if unclear.
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
Contactor drops out on its own / won't stay latched
The contactor pulls in when you press start but drops out the moment you release the button, or randomly during running — the seal-in (latch) isn't holding it.
Auxiliary contact not making — seal-in or interlock fails
The contactor pulls in, but an auxiliary contact (used for seal-in, interlock, or status) doesn't change state, so the circuit won't latch, an interlock misbehaves, or status feedback is wrong.
Motor goes one way but won't go the other (e.g. down but not up)
A reversing drive works in one direction only. One command (say, down) runs fine; the other (up) does nothing, or just hums/trips. Common on hoists, doors, and conveyors.