The display shows E4 and the machine will not start extraction; the recovery tank is nearly full.

Safety first: Unplug the machine before removing tanks or covers.

• Empty recovery tank: Remove and fully empty the dirty water (recovery) tank. Rinse it thoroughly to remove foam, detergent residue, and debris.
• Clean float mechanism: Locate the float or level sensor assembly inside the recovery tank lid or body. Ensure the float moves freely up and down. Clean off any sludge or scale.
• Check sensor wiring: Inspect the wiring from the tank sensor to the main body connector. Look for broken wires, corrosion on terminals, or loose plugs. Reseat connectors firmly.
• Check for foam: Excess foam from over-dosing detergent can trigger the full sensor. Use a defoamer in the recovery tank if recommended by Numatic, and reduce detergent concentration.
• Test operation: Refit the tank correctly, ensuring it is fully seated and any magnetic or mechanical sensor alignment points are correctly positioned. Plug in and test.
• If E4 persists: The level sensor or the input circuit on the control PCB may be defective and should be tested and replaced by a qualified technician.