Machine displays A4 and stops; water tank icon may flash and no brewing is possible.

Safety first: Turn OFF and unplug the machine before inspecting internal sensors.

Step 1 – Check tank position and fill level

• Remove the water tank, rinse it, and fill to at least the minimum mark.
• Inspect the bottom valve for damage or stuck position; press it gently to ensure it moves freely.
• Reinstall the tank firmly until it clicks or sits flush with the body.
• Power the machine ON and see if A4 clears.

Step 2 – Inspect float and magnet (if equipped)

• Look inside the tank for a plastic float; it should move freely up and down.
• Shake the tank gently; if the float is stuck, soak the tank in warm water with mild detergent and rinse.
• If the float contains a magnet, ensure it is not cracked or filled with water; replace the tank if the float is defective.

Step 3 – Clean sensor area

• On the machine body, locate the level sensor area (often a small window or recess where the tank sits).
• Wipe the area with a soft damp cloth to remove scale or coffee residue.
• For optical sensors, ensure the window is clear and not scratched.

Step 4 – Internal sensor check (advanced)

• Unplug the machine and remove the cover.
• Locate the reed switch or optical sensor near the tank area.
• Check wiring for loose connections or damage.
• If a reed switch is used, test it with a magnet (with the machine unplugged) to see if it clicks or changes continuity (requires multimeter).

When to seek service

• If A4 persists with a known-good tank and clean sensor area, the internal level sensor or control board may be faulty.
• Contact a service center for sensor or board replacement.