Connect each sensor
correctly
Replace flow sensor
Replace TC sensor
Miswiring between
flow sensor connector (CN609)
and low pressure sensor
connector (CN607)
Flow rate detected by
flow sensor is almost same
as actual value
Start
Water flow is detected
by flow sensor during no
pump P1 operation
No
No
Yes
TC sensor
characteristic is correct
Yes
No
Replace flow sensor
Flow rate detected by
flow sensor is almost same
as actual value
Yes
No
Yes
Yes No
Identify the cause and resolve it
ex.) Flow due to the external pump
Check water heat exchange control board
If defective, replace it
PC board
MCC-1753