The display shows E8, and the dirty water tank full icon is flashing even when the tank is empty.

Safety first: Unplug the carpet cleaner before removing the dirty water tank.

• Remove and clean dirty tank: Take out the dirty water tank and lid. Rinse thoroughly with warm water. Pay special attention to the float chamber and any small openings.
• Free the float: Locate the float (usually a plastic piece that moves up and down). Ensure it moves freely. If stuck with dried detergent or debris, soak and gently clean until it moves smoothly.
• Check tank seating: Refit the tank, ensuring it sits flat and clicks into place. A misaligned tank can falsely trigger the full sensor.
• Inspect full sensor: On some Vax models, a small switch or optical sensor detects the float position. Check for dirt on the sensor window or mechanical switch. Clean gently with a soft cloth.
• Replace tank lid or sensor: If the float mechanism is damaged or the sensor does not respond, replace the dirty water tank lid assembly or the full sensor module as appropriate.