Pump will not start, only a humming sound is heard for a few seconds

Safety first: Turn off power immediately if the motor only hums; prolonged humming can burn out windings.

• Check shaft rotation: With power off, try to rotate the motor shaft or fan by hand. If it is stiff, investigate for seized bearings or impeller blockage.
• Inspect and test capacitor: Access the capacitor compartment on the Calpeda motor, visually inspect for bulging or leaks, and test capacitance with a meter. Replace if out of tolerance.
• Examine start switch: On motors with a centrifugal start switch, inspect for stuck or burnt contacts. Clean or replace as necessary (this is often a job for a motor repair shop).
• Verify supply voltage: Measure voltage at the motor terminals during start. If it drops significantly, check for undersized wiring or overloaded circuits.