Mars Comfort-Aire Century VCD-SA Series Service Manual page 126

S Communication:
Power off, then restart the unit after 2
minutes.
Does the error code
disappear?
Yes
Check the wiring connection
between indoor and outdoor
unit, are they good?
Yes
Measure the DC voltage between N/L2
and S (Black pin to S , Red pin to N/L2).
For units with main PCB and IPM board
Check the AC voltage of L, N
output to IPM board, is it same
as power input?
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?
No
Check the DC 5V, 12V
from IPM board to main
PCB, are they normal?
No
Unplug electronic expansion valve.
Check if the DC 5V, 12V to main
PCB are OK
No
Replace IPM board
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.
No Solved
Correct the connection or
No
change wires
The value is alternative
from negative to positive
The value is fixed and close
to 0
The value is always positive
both
No Replace main PCB
Replace short-circuited
Yes component and main
PCB
Yes
Replace short-circuited
component and outdoor
PCB
Replace coil of electronic
Yes
expansion valve
 Troubleshooting 23
Check the wiring connection
from indoor terminal to indoor
PCB, are they good?
For units with only one
Check the wiring connection
PCB
Replace outdoor PCB Yes
components connected to main
PCB such as 4 way valve, heater,
Yes
AC fan one by one to check their
resistance. Is there any component
No
Unplug electronic expansion valve.
Yes

Service Manual - VCDxxSA
Repalce indoor PCB
from outdoor terminal to
outdoor PCB and wiring
between PCBs if there is
more than 1 PCB
Check if the power LED is
on?
No
Unplug all the high voltage
short circuit?
No
Check if power LED is on?