Does the error code disappear?
Power o , then restart the unit after 2
minutes.
Measure the DC voltage between N/L2
and S (Black pin to N/L2, Red pin to S).
The value is xed and close
to 0.
The value alternates from
negative to positive.
The value is always positive.
Check the
wiring connection
between the indoor and outdoor
unit. Are they good?
If there is more than 1 PCB,
check the wiring connection
from the outdoor terminal to
the outdoor PCB and the
wiring between PCBs.
Check the wiring connection
from the indoor terminal to the
indoor PCB. Are they good?
Turn on the unit, check if W
and 1 (L) are connected.
Check if the power LED is on.
Yes
Yes
Yes
Unplug electronic expansion valve.
Check if power LED is on.
No
No
Check the AC voltage of L, N
output to IPM board. Is it the
same as the power input?
Check the DC 5V, 12V
from IPM board to main
PCB. Are they normal?
Unplug all the high voltage
components connected to the
main PCB such as 4-way valve, heater,
and AC fan (one by one) to check
their resistance. Has any component
short-circuited?
Yes
No
Unplug electronic expansion valve.
Check if the DC, 5V, 12V to main
PCB are in working order.
Replace the short-circuited
component and the
main PCB.
Replace the electronic
expansion valve coil.
Replace the outdoor PCB.
Yes
Yes
Yes
Replace the
main PCB.
No
No
Replace the IPM board.
No
Replace indoor PCB.
No
Solved
Correct the connection or
change wires.
No
No
Yes
For units with a main PCB and IPM board
(both)
For units with only one PCB.
For units with
a W wire
For units without W
wire
No
Replace the short-circuited
component and the
outdoor PCB.
Unplug all the high voltage
components connected to the
main PCB such as 4-way valve, heater,
and AC fan (one by one) to check
their resistance. Has any component
short-circuited?
Yes
Yes
NOTE: For certain models, the outdoor PCB can not be removed separately.
In this case, the outdoor electric control box should be replaced as a whole.
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