Safety: Unplug the carpet cleaner. The vacuum motor is a high-voltage component.

Check tank interlock: Ensure the dirty water recovery tank and lid are fully seated. Many Stihl units have a tank presence switch that prevents vacuum operation if the tank is not installed correctly.
Inspect wiring: Remove the motor housing cover and locate the vacuum turbine motor. Confirm the wiring harness plug is fully inserted and there are no burnt connectors.
Listen for motor: If the motor hums but does not spin, the capacitor (if present on an external bracket) may be faulty. A bulged or leaking capacitor should be replaced with the same µF rating and voltage.
Check for burning smell: A strong burnt odor or visible black dust around the motor vents indicates worn brushes or a failed motor. In this case, the motor assembly should be replaced rather than repaired.

Because of shock and fire risk, full motor replacement should be done by a qualified technician if you are not experienced with mains-powered motors.

Vacuum motor does not start; display shows E04 when trigger is pulled

Possible Causes