Carrier 38MBQ Series - IPM Malfunction Diagnosis; Troubleshooting PO Error

27
DIAGNOSIS AND SOLUTION (CONT)
Table 23—IPM Malfunction or IGBT Over−strong Current Protection Diagnosis and Solution (PO)
Error Code PO
Malfunction Decision Conditions
When the voltage signal that IPM sends to the compressor drive chip is abnormal, the LED
displays “PO” and the AC turns off.
Supposed Causes
S Wiring mistake
S IPM malfunction
S Outdoor fan assembly faulty
S Compressor malfunction
S Outdoor PCB faulty
Troubleshooting
Check the wiring between main PCB
and compressor. Is there an error?
Ensure a proper connection or
replace the wires and connectors
Yes
No
Check the IPM. Is it in working
order?
No
Yes
Replace the IPM board or replace
the main PCB
Check the outdoor fan and the
outdoor unit ventilation. Is it in
working order?
No
Please refer to the solution
“fan speed is out of controlā
malfunction
Yes
Check the compressor resistance
values. Are they within acceptable
parameters?
No
Replace the compressor
Yes
Replace the outdoor main PCB
NOTE: In figures 21−24 the following is observed:
S U,V,W references the compressor connection point
S P references input voltage
S N references output voltage