AO Smith
Failed Start Capacitor or Centrifugal Switch (Single-Speed / Two-Speed Motors)
AO Smith pool pump hums but will not start; motor housing gets warm and then shuts off.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Open or weak start capacitor, Stuck centrifugal start switch inside motor, Burned start winding, Low supply voltage preventing proper start torque
How to Fix / Troubleshooting
Safety First: Turn OFF power at the breaker and verify zero voltage before opening the motor. Capacitors can hold a charge—discharge them safely.
- Check shaft rotation: With power OFF, remove the rear cover and try to spin the motor shaft or fan by hand. If it spins freely, the issue is likely electrical (capacitor/switch).
- Inspect start capacitor: Locate the capacitor can on top or side of the motor. Look for bulging, leaking oil, or burn marks. Replace with an AO Smith-rated start capacitor of identical µF and voltage rating.
- Test start assist: Briefly turn power ON and gently spin the shaft with an insulated tool (if safely accessible). If the motor starts and runs, the start circuit is faulty.
- Service centrifugal switch: For motors with an internal start switch, inspect contacts for burning or sticking. Clean or replace the switch assembly if accessible.
- Verify voltage: Measure line voltage under load to ensure it meets the motor nameplate. Correct wiring or breaker issues if low.
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Repair Difficulty
Medium
3/5
Required Part
Start Capacitor
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