Reversing starter trips when changing direction
The drive runs each direction on its own but trips protection when you change from forward to reverse (or vice versa), often if the changeover is too quick.
Safety first
Reversing a spinning motor (plugging) draws very high current and stresses the drivetrain. Ensure the load can take it and the area is clear before testing changeovers.
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
No off-delay between directions (plugging)
Most likelySwitching straight from forward to reverse while the motor is still spinning causes a huge current surge that trips protection.
- 2
Interlock timing too tight
#2The changeover interlock isn't allowing the first contactor to fully drop before the second closes.
- 3
Both contactors briefly closing
#3A failed or mis-wired interlock lets both direction contactors close together momentarily, creating a phase-to-phase fault.
- 4
High load inertia
Least likelyA high-inertia load takes longer to stop, so an immediate reverse plugs hard and trips.
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.
Check whether the control allows the motor to stop (or an off-delay) before reversing.
A stop/off-delay between directions so the motor isn't reversed while spinning.
There's a delay — check the interlock timing and wiring.
No delay — direct plugging is causing the trip; add a delay or stop step.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Trips on direction change
→ step 2 - 2decision
Is there a stop/off-delay before reversing?
Yes→ step 3No→ step 4 - 3decision
Does the interlock let one contactor fully drop before the other closes?
Yes→ step 5No→ step 6 - 4result
Direct plugging — add a stop step / off-delay.
- 5result
Review load inertia / changeover method.
- 6result
Overlapping changeover — correct the interlock (never bypass).
Common mistakes apprentices make
- Allowing direct forward-to-reverse switching while the motor is still spinning.
- Defeating or weakening the changeover interlock to 'fix' nuisance trips.
- Ignoring high load inertia that needs a stop before reverse.
- Not confirming both contactors can't close together.
When to stop & escalate
The forward/reverse interlock prevents a dangerous phase-to-phase fault — never bypass it. If the application genuinely needs rapid reversing, the changeover method should be designed for it (e.g. controlled stop), not forced.
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.
Forward/reverse interlock locking out both directions
Neither direction will run — the interlock that stops both contactors closing together appears to be holding everything off, so no movement at all.
Motor overload keeps tripping
The thermal/electronic overload trips repeatedly, either on start or after the motor has run for a while. Resetting only buys you a short run before it trips again.
Learn the theory
How the gear and circuits behind this fault actually work.