Pump hums loudly when switched on but the motor shaft does not turn and no water is circulated.

Safety first: Turn off power immediately if the pump hums but does not start; prolonged humming can overheat the motor.

• Check for free rotation: With power off, remove the rear fan cover and attempt to rotate the motor shaft by hand. If it is stiff or locked, the bearings or impeller are seized.
• Inspect for debris: Remove the pump lid and basket, then check inside the volute for stones, tiles, or other obstructions blocking the impeller.
• Test/replace capacitor: On models with an external capacitor canister on the motor, have a technician test the start capacitor and replace it with the correct Emaux-rated value if faulty.
• Avoid repeated restarts: Do not keep trying to start a stalled motor; this can burn out the windings.

If the shaft is free but the motor still only hums, the start winding or internal switch is likely damaged and the motor assembly should be replaced.