Haier HBU-18HF03 Manual page 248

6) Sensor failure
check if the wiring is correct
according to wiring diagram
if sensor is fixed well
Is sensor short-circuit or open-circuit?
Is sensor resistance acceptable?
Is DC voltage between both
ends of sensor near 5V or 0V?
Replace PCB
5) Communication error between indoor and outdoor units
Confirm commumication failure
according to the fault code list
Confirm the fault indicator is communication failure
Does indoor communication indicator flash?
Are communication wire S and supply wires L
and N properly connected? Grounded well?
if communication wire is broken
check if indoor/outdoor PCB fuse
and transformer are normal
replace indoor PCB
if failure is eliminated
no
reconnect
yes
no
Relocate
yes
yes
yes
no
yes
no
yes
no
yes
no
no
yes
no
replace outdoor PCB
Replace sensor
Replace sensor
no
re-wiring
yes
re-wiring
change
defective parts
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Troubleshooting