Motor runs in the wrong direction
The motor runs but the wrong way — pump runs backwards, fan blows the wrong way, conveyor reverses. Usually a phase-rotation issue after wiring or supply work.
Safety first
Reversing phases means working at live-capable terminals — isolate and prove dead first. Check that running the wrong way hasn't already damaged the driven equipment.
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
Two phases swapped (wrong rotation)
Most likelySwapping any two of the three phases reverses a three-phase motor — common after rewiring or supply changes.
- 2
Wrong rotation from the supply / after supply work
#2If incoming phase rotation changed, every motor fed from it can run the wrong way.
- 3
Miswired reversing starter
#3On a reversing setup, the forward/reverse contactors or their wiring are swapped.
- 4
Single-phase motor wired for the wrong rotation
Least likelySingle-phase motors reverse by swapping the start-winding connections; these may be wrong.
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.
Confirm the required direction, then check phase rotation at the motor terminals (or note the recent change).
Phase rotation matches the direction the equipment needs.
Rotation is correct here — check the starter wiring / single-phase connections.
Reversed rotation — swap two phases to correct it.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Motor runs wrong way
→ step 2 - 2decision
Is phase rotation at the motor correct for the needed direction?
Yes→ step 3No→ step 4 - 3decision
Is the reversing/starter (or single-phase) wiring correct?
Yes→ step 5No→ step 6 - 4result
Reversed rotation — swap two phases to correct.
- 5result
Re-verify supply rotation and any recent upstream change.
- 6result
Swapped starter / start-winding wiring — correct it.
Common mistakes apprentices make
- Swapping phases at random instead of confirming rotation first.
- Not checking whether the supply rotation changed after upstream work.
- Forgetting that single-phase motors reverse via the start winding, not by swapping line/neutral.
- Running a pump/fan backwards long enough to damage it.
When to stop & escalate
If the whole supply rotation has changed, confirm the wider impact before swapping everything — coordinate so all affected equipment is corrected consistently. Check the driven equipment hasn't been damaged by reverse running.
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
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.
Three-phase equipment single-phasing (lost a phase)
Three-phase equipment is misbehaving — motors humming, struggling, overheating, or tripping — because one phase has been lost somewhere between the supply and the load.
Phase-failure / monitoring relay has tripped the circuit
A phase-failure or phase-sequence monitoring relay has dropped out and is holding the control circuit off, stopping the equipment — even though the panel looks powered.
Learn the theory
How the gear and circuits behind this fault actually work.