Midea MCH2U-18PHH2, Service Manual

Page: 90 / 131

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IPM module protection
Check whether the voltage range
of P-N on IPM module is normal?
DC277-356V for 18-27KBtu/h;
DC277-410V for 36KBtu/h
Yes
Yes
No
Yes
Check whether the input
power supply is correct?
208-230V, 1N, 60Hz
No No
Regulate it to correct, then
check whether the system
can work normally?
Check whether the
power supply line is
connected correctly and
tightly
Yes
Connect it correctly
and tightly, check ok
or not?
No
Check whether the connecting
line between main board and
the IPM module is connected
tightly
Yes
Connect it tightly,
check ok or not?
No
No
No
Connect it well, check
ok or not?
Check whether the connecting
line of the compressor is
connected correctly or tightly
Replace the IPM module,
check whether the system can
work normally?
No
No
Replace the main board; check
whether the system can work
normally?
No
Replace the compressor, check
whether the system can work
normally?
Check whether the lines
in E-part box are
connected tightly
Yes
Connect it tightly,
check ok or not?
No
No
Yes
No
Replace the bridge rectifiers
Check whether the bridge rectifiers are
normal? Use the multimeter to measure
the resistance between each two
terminals, check whether there is the
condition that value of resistance is 0
Check whether the connecting line of
every reactor is normal? If the line is
broken, the resistance of the two ports is
∞
（
models except for M4OC-36HRFN1-
M
）；
Check whether the PFC module
broken (for M4OC-36HRFN1-M)
Replace the connecting line or
reactor or replace the PFC
module(for M4OC-36HRFN1-M)
Yes
No
No
Yes
Trouble is solved
Check if the outdoor fan
runs properly or the outdoor
unit ventilation is good.
No
For M3OD-27HRDN1-M, please
refer to 8.5 Trouble Criterion Of
Main Parts, check whether the
resistance of the fan motor is
normal. If not, replace the fan
motor.
For other models, r
efer to
the solution of fan speed has
been out of control
malfunction . Find out the cause
and have it solved.
Yes
Yes
Yes