Carrier 42QHP09E8S Service Manual page 78

5.12 P4(Inverter compressor drive error diagnosis and solution)
Description: An abnormal inverter compressor drive is detected by a special detection circuit, including communication
signal detection, voltage detection, compressor rotation speed signal detection and so on.
Recommended parts to prepare:
• Wiring mistake
• IPM malfunction
• Faulty outdoor fan assembly
• Compressor malfunction
• Faulty outdoor PCB
Troubleshooting and repair:
Check the wiring between the
the outdoor unit ventilation.
 Page 74 
PCB and compressor.
Is it improperly wired?
NO
Check the IPM.
Is it functioning
properly?
YES
Check the outdoor fan and
Is it functioning
properly?
YES
Check the compressor
resistance values.
Are they within
acceptable parameters?
YES
Replace the outdoor PCB.
Ensure proper connections or replace
YES
the wires and connectors.
Replace the IPM board or
NO
replace the outdoor PCB.
Please refer to "Fan
NO
Speed Malfunction"
NO Replace the compressor.