Airwell VVFA Series Service Manual page 53

[35] 4-way valve reversing failure
If connection between 4-way valve
and connecting board is good
If system meets condition
of 4-way valve reversing:
Pd-Ps>0.6MPa
Measure if CN49 voltage
on connecting board is
220VAC after 4-way valve
reversing condition is met
If compressor running
current is normal
If there is air noise after 4-way
valve reverses, and if the temp. of
connection pipes with 4-way valve is
normal
Replace 4-way valve
Yes
Yes
Yes
Yes
No
No
No
No
No
51
Re-connect
Check if SV1 leaks
Replace connecting board
Check compressor