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Installation and Maintenance
Service Manual
5. Out of step diagnosis for the compressor (AP1 hereinafter refers to the control board of the outdoor unit)
Mainly detect:
●Is the system pressure too high?
●Is the input voltage too low?
Fault diagnosis process:
Out of step occurs once the 
unit is powered on.
Is stop time of the 
compressor longer than 
3 minutes?
Are the wires for the compressor connected 
correctly? Is connection sequence right?
Is the connection made in clockwise 
direction?
Connect the 
wires correctly
Replace the control 
panel AP1
If the fault is eliminated?
Replace the 
compressor 
End
Out of step occurs in 
operation
Is the outdoor fan working 
normally?
Is the outdoor unit blocked 
by foreign objects?
Replace the 
control panel AP1
If the fault is eliminated?
Replace the 
compressor 
End
Check if the fan terminal 
OFAN is connected correctly
Remove foreign objects
Replace the fan 
capacitor C1
Replace the 
outdoor fan
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes