Bosch Singular 4000 - 8 Troubleshooting; A2 Error (Abnormal Operation: Fan)

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Service Manual
Singular Combi Boiler - BTC 439002301 A (12.2021)
8 Troubleshooting
8.1 A2 Error (Abnormal Operation: Fan)
Error Description
Turbo fan RPM error Error occurs when the RPM is not measured due to no turbo fan operation or a defect of the hall sensor
Checkpoint
 Check the connection of the wire
 Check the fan wire for disconnection
 Check the PCB output voltage
— Red-Black: 0 – 45 V
— Yellow-Black: 0 – 13 V
Table 23
Figure 5
Check the assembly
condition of the control board
and the fan connector.
Reassemble the control board
and the fan connector.
Replace the control board
Replace the fan
Replace the fan
Replace the control board
Power ON / faucet ON
(1 GPM)
Check
the fan input
voltage
Fan operation
Check
the FAN Hz
Ye s
Ye s
Ye s
No
No
No
Red-Black: 5 45 V
Black-Yellow: 10 13 V