Haier Unitary smart series Service Manual page 180

9.3 Troubleshooting for fixed frequency units
1) Pressure protection
Confirm the fault according
to the fault code list
Does system have
pressure switch?
yes
Is actual pressure detected by
pressure gage acceptable?
no
low pressure failure
yes
Is high pressure too low?
yes
Refrigerant charge is
needed. Check if there is
refrigerant leak. If yes,
replace pipe.
Note: The confirmation time of low pressure failure may be shorter, but high pressure failure confirmation
time is at least 1 hour. Besides, take the ambient temperature into consideration.
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2) Sensor failure
check if the wiring is
correct according to
wiring diagram
no
if sensor is fixed
well
yes
Is sensor short-circuit
or open-circuit?
yes
Is sensor resistance
acceptable?
yes
Is DC voltage between
both ends of sensor
near 5V or 0V?
no
Replace PCB
no
Are CN17 and CN18
in PCB cut off?
yes
Make them in
short circuit
yes
Change pressure
switch
no
high pressure failure
no
is pipe blocked?
dredge piping
no
reconnect
Relocate
yes
Replace sensor
no
Replace sensor
a__
no
Replace PCB
yes
yes
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