Display shows “Error 12”; machine may not detect the water tank or may think it is empty when full.

Safety first: Unplug the machine before opening the housing.

Step 1 – Check water tank magnet:

• Remove the water tank and inspect the area where the magnet is embedded (often a small cylinder or strip).
• If the magnet is missing or loose, replace the water tank.

Step 2 – Clean sensor area:

• Clean the area on the machine where the tank sits; coffee or scale deposits can interfere with sensor operation.

Step 3 – Test with another tank (if available):

• If you have access to another compatible Jura tank, test whether the machine recognizes it.

Step 4 – Internal sensor check (advanced):

• Remove the housing (unplug first).
• Locate the reed switch or Hall sensor near the tank area.
• Check wiring and connector to the main board.
• Test the reed switch with a magnet and multimeter for open/close operation.

Step 5 – Replace faulty parts:

• Replace the water tank if the magnet is missing or weak.
• Replace the reed switch/Hall sensor if it does not respond to a magnet.
• If the board does not register a working sensor, the main control board may need replacement.