Bosch TCA640 Series Repair Instruction page 73

7.2.2 System messages
7.2.2.1 Add water
ADD WATER
Water tank is empty
(1) The water level in the tank is monitored by a float
with magnet (A) / magnetic switch and software counter
(pulses from flowmeter) in the appliance.
(2) When the water tank has been filled, the float rises
and actuates the magnetic switch.
►
The appliance is ready to use.
(3) If the water level drops to a level between 80 ml and 180 ml,
ADD WATER is displayed. The amount of residual water in the tank
depends on the product which was last brewed (espresso, coffee...).
Brewing is not terminated due to lack of water.
(4) Silting or calcification in the water tank may cause the float to
stick to the tank wall. Despite the filled tank, the ADD WATER
display does not go out.
The incorporation of additional guide fins (B) for the float reduces
the risk of the float sticking.
58300000120060_ARA_en_c.doc – 18.09.09 Seite 73 von 95