Carrier 42QHF012DS Service Manual page 67

Voltage protection
Check the voltage of
outdoor unit power supply,
whether the voltage
between L(L1) and N (L2) is
about 220~240VAC
Yes
Check whether the voltage
of IPM board P and N is
normal? DC277-356V for
18-27KBtu/h; DC277-410V
for 36-42KBtu/h
No
Replace bridge rectifiers,
and then check whether the
system can run normally
No
Replace IPM board, and
then check whether the
system can run normally
No
Replace outdoor main board
No Check the power supply
Yes
Yes
Yes
Trouble is solved
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