Carrier 38MBRC Series Service Manual page 19

38MBRC: Service Manual
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 the
same as the power input?
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?
Check the DC 5V, 12 V
from IPM board to main
PCB, are they normal ?
Unplug electronic expansion valve.
Check if the DC 5V, 12 V to main
PCB are OK
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.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
No
Correct the connection or
No
change wires
The value is alternative
from negative to positive
The value is fixed and close
The value is always positive
For units without W
wire
Check the wiring connection
from outdoor terminal to
both
outdoor PCB and wiring
between PCBs if there is
more than 1 PCB
No Replace main PCB
Yes
Yes
Yes
No
No
Yes
No
Solved
Check the wiring connection
from indoor terminal to indoor
to 0
PCB, are they good ?
For units
with W wire
Yes
For units with only one
PCB
Replace outdoor PCB
Replace short -circuited
component and main
PCB
Replace short-circuited
component and outdoor Yes
PCB
No
Replace coil of electronic
Yes
expansion valve
19
Repalce indoor PCB
Turn on the unit , check if W
and 1(L) is connected?
Yes Check if the power LED is on.
No
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
Unplug electronic expansion valve.
Check if power LED is on.
No