Bosch TCA640 Series Repair Instruction page 89

7.5.6 Brewing unit is not functioning
Fault description:
Brewing unit no longer moves
Possible faults:
1. No control signal voltage from logic module
2. No voltage at power module brewing unit output
3. No voltage at brewing unit drive input
Troubleshooting:
1. Check control signal voltage from logic module
To do this, open the appliance. Using the Torx T10 screwdriver,
unscrew all rear panel screws and remove the rear panel. Remove
upper appliance cover to the rear. Remove both side panels upwards.
Check two control signals for the brewing unit. Signal on right =
brewing unit runs up; signal on left = brewing unit runs down. The
control signal voltage on the right is measured on plug CL10 terminal
1 = GND (brown) and terminal 6 = 5 VDC (blue); the control signal
voltage on the left is measured on CL10 terminal 1 = GND (brown)
and terminal 7 = 5 VDC (violet). The brewing unit must be actuated by
a coffee brewing process.
►
No control voltage on right
cable defective
►
No control voltage on left
defective
→
►
Voltage available
58300000120060_ARA_en_c.doc – 18.09.09
→
Logic module or connecting
→
Logic module or connecting cable
see Point 2
2. Check voltage on power module brewing unit output
To check the voltage at the power module brewing unit output (=12
VDC), open the appliance. Using the Torx T10 screwdriver, unscrew
all rear panel screws and remove the rear panel. Remove upper
appliance cover to the rear. Remove both side panels upwards.
The voltage for the drive of the brewing unit is measured on plug
CP2A on terminals 1-green and 2-red.
For operation on right = brewing unit runs up;
green = GND / red = 12 VDC
For operation on left = brewing unit runs down;
green = 12 VDC / red = GND
The brewing unit must be actuated by a coffee brewing process.
→
►
No voltage defective power module
→
►
Voltage available
3. Check voltage on brewing module drive input
The operating voltage of the brewing unit drive is checked on the
terminals of the motor. To conduct this measurement, detach the drive
from the appliance.
The operating voltage can be measured on the terminals of the motor.
→
►
No voltage defective wiring
→
►
Voltage available
see Point 2
defective brewing unit drive
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