Xtreme MSAGBU-09HRFN8-QRD1GW, Service Manual, Page: 143 / 183

 Troubleshooting 
TS02-S-INV: Indoor and outdoor unit communication error diagnosis and solution
Description : Indoor unit can not communicate with outdoor unit
Recommended parts to prepare:
• Indoor PCB
• Outdoor PCB
• Short-circuited component
Troubleshooting and repair:
Does the error code
disappear?
Power off, 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 fixed and close
to 0
The value is alternative
from negative to positive
The value is always positive
Check the wiring connection
between indoor and outdoor
unit, are they good?
Check the wiring connection
from outdoor terminal to
outdoor PCB and wiring
between PCBs if there is
more than 1 PCB
Check the wiring connection
from indoor terminal to indoor
PCB, are they good?
Turn on the unit, check if W
and 1(L) is connected?
Check if the power LED is
on?
No
Yes
Yes
Unplug all the high voltage
components connected to main
PCB such as 4 way valve, heater,
AC fan one by one to check their
resistance. Is there any component
short circuit?
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 same
as power input?
Check the DC 5V, 12V
from IPM board to main
PCB, are they normal?
Unplug all the high voltage
components connected to main
PCB such as 4 way valve, heater,
AC fan one by one to check their
resistance. Is there any component
short circuit?
Yes
No
Unplug electronic expansion valve.
Check if the DC 5V, 12V to main
PCB are OK
Replace short-circuited
component and main
PCB
Replace coil of electronic
expansion valve
Replace outdoor PCB
Replace short-circuited
component and outdoor
PCB
Yes
Yes
Yes
Yes
Replace main PCB No
Yes
No
Replace IPM board
No
Repalce indoor PCB
No
Solved
Correct the connection or
change wires
No
Yes
Yes
For units with main PCB and IPM board
both
For units with only one
PCB
For units
with W wire
For units without W
wire
No
Note: For certain models, outdoor PCB could not be removed separately. In this case, the outdoor electric
control box should be replaced as a whole.