Safety: Turn off power at the breaker before touching any pump or wiring.

Listen for pump behavior: Restore power and start the affected pump. If it hums but does not turn, or trips F4 immediately, turn power off again.
Check for obstructions: With power off, remove the pump union on the suction side of the Villeroy & Boch jet pump and inspect for debris at the impeller. Clear any obstruction and reassemble.
Spin test: Try to rotate the pump shaft (from the rear fan or coupling) by hand. If it is seized or very stiff, the pump motor likely needs replacement.
Inspect wiring and connections: Verify that the pump’s power cable is intact and firmly connected to the control pack. Look for burn marks or melted connectors.
Relay check (advanced): If you are qualified, inspect the pump relay on the Villeroy & Boch control board for signs of overheating or pitting. A stuck relay can cause F4 and should be replaced with the correct OEM board.

Due to electrical hazards and high current, pump and relay replacement should generally be performed by a spa technician.

F4 error, pumps may not start or may shut off shortly after starting

Possible Causes