E13 appears and the unit shuts down when the dirty water tank is nearly full, even though the tank is not yet at the max line.

Safety first: Disconnect from mains before working on the tank or sensor.

• Empty and clean dirty tank: Remove the recovery tank, empty it completely, and rinse with warm water. Ensure the float chamber is free of sludge and fibers.
• Check float movement: Move the float up and down by hand. It should move smoothly without sticking. Clean any buildup that may cause friction.
• Inspect float for damage: If the float has absorbed water or is deformed, it may trigger the sensor early. Replace the float assembly.
• Test level switch: If the sensor is a microswitch or reed switch, test continuity while moving the float. Replace the switch if it does not change state correctly.

Always keep the dirty tank below the maximum fill line to avoid overflow into the motor compartment.