Carrier 42QHC009DS Service Manual page 38

9.2.6 IPM malfunction or IGBT over-strong current protection diagnosis and solution(P0)
Error Code
Malfunction decision
conditions
Supposed causes
Trouble shooting:
Check the wiring between main PCB
and compressor
Check the IPM
Check the outdoor fan and the
outdoor unit ventilation
Check the compressor resistance
Replace the outdoor main PCB

IPM continuity check
Turn off the power, let the large capacity electrolytic capacitors discharge completely, and dismount the IPM. Use a digital
tester to measure the resistance between P and UVWN; UVW and N.
Digital tester
(+)Red (-)Black
N
U
P
V
W
P0
When the voltage signal that IPM send to compressor drive chip
is abnormal, the display LED will show "P0" and AC will turn off.
Wiring mistake
●
IPM malfunction
●
Outdoor fan ass'y faulty
●
Compressor malfunction
●
Outdoor PCB faulty
●
No
Yes
Yes
values
Yes
Normal resistance value
∞
(Several MΩ)
Correct the connection or replace
Yes
the wires and connectors.
Replace the IPM board or replace
No
the main PCB
Please refer to the solution of 【Fan
No
Speed Has Been Out Of Control】
No Replace the compressor.
Digital tester
(+)Red (-)Black
U
V
N
W
(+)Red
36
malfunction
Normal resistance value
∞
(Several MΩ)