Haier AB422XCBAA Service Manual page 165

9) Low pressure protection
Confirm the fault according
to the fault code list
yes
Are connectors of pressure switch in good
condition?
yes
Is low side pressure switch
activated? (If not, DC voltage is 0V.)
yes
Is the low side pressure detected by
the gage lower than threshold value?
The threshold value is indicated on
the switch
yes
if outdoor stop valves of gas pipe
and liquid pipe are open totally
yes
Is piping twisted or deformed?
no
Does indoor fan work properly during
cooling cycle? Does outdoor fan work
properly during heating cycle?
yes
Is indoor filter or heat
exchanger dirty?
no
Measure equalized pressure and time to
reach equalization to see if the system has
leakage. Lack of refrigerant? Is capillary
blocked?
no
Bad operation codition, such as ultra low
outdoor temperature
no
Check and reconnect
no
Replace PCB
no
Replace low pressure
switch
no
Open the valves
yes
Repair pipe
no
Repair fan motor or fan
capacitor
yes
Cleaning
yes Conduct leak test.
Evacuate and recharge
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