Carrier 38MGRBQ18B-3 Service Manual page 42

38MGRBQ: Service Manual
DIAGNOSIS AND SOLUTION (CONT)
Over-voltage or under-voltage protection diagnosis and solution
ERROR CODE
MALFUNCTION DECISION
CONDITIONS
SUPPOSED CAUSES
Troubleshooting
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
E5, PC 10, PC 11 OR PC 12
When the supply voltage to the unit or to the main control board is outside the acceptable tolerance, the unit's
LED displays E5, PC 10, PC 11 or PC 12 and then the unit turns off.
Issues with supply voltage
Wiring mistake
IPM malfunction
Faulty outdoor PCB
Voltage protection
Check the voltage of
outdoor unit power supply,
whether the voltage
between L(L1) and N (L2) is
about 187~253VAC
Yes
Check whether the voltage
of IPM board P and N is
normal: DC277-356V for
18-27KBtu/h; DC277-410V
for 36KBtu/h
No
Replace bridge rectifiers
and then check whether the
system can run normally
(Only for qua-zone).
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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