Carrier 40MAHB Series Service Manual page 17

40MAHB: Service Manual
DIAGNOSIS AND SOLUTION (CONT)
Indoor and Outdoor Unit Communication Error (EL01)
Description: The indoor unit cannot communicate with the outdoor unit
Recommended parts to repair:
• Indoor PCB
• Outdoor PCB
• Short-circuited component
Troubleshooting
Power off, then restart the unit after 2
Does the error code
Check the wiring connection
between the indoor and
Measure the DC voltage between N/L2
and S (red pin to N/L2, black pin to S).
For units with main PCB and IPM board both.
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 (4 way valve, heater, AC fan)
one by one to check their resistance.
Has any component short circuited?
Unplug electronic expansion valve.
Check if the DC 5V, 12V to the main
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.
minutes.
disappear?
between the indoor and outdoor
Correct the connection or
No
change wires.
outdoor units.
Are they OK?
The value is alternative
from negative to positive.
Yes
The value is fixed and close to 0.
The value is always positive
For units without W wire
Check the wiring connection
from outdoor terminal to
outdoor PCB and wiring
between PCBs if there is
more than 1 PCB
Replace the
No
main PCB.
Yes
Yes
Yes
No
Check the DC 5V, 12V
from IPM board to main
PCB. Are they OK?
No
Yes
PCB are ok.
No
Replace the IPM board.
Solved
Check the wiring connection
from indoor terminal to indoor
PCB. Are they OK?
For units
with W wire
Turn on the unit, check if W
and 1(L) are connected.
Yes
For units with only one PCB
Replace the
Yes
outdoor PCB.
Replace short-circuited
component and main
PCB.
Replace the short
-circuited component Yes
and the outdoor PCB.
No
PCB
Replace the electronic
Yes
expanson valve coil.
17
Replace the
indoor PCB.
No
Check that the power
LED is on.
No
PCB
Unplug all the high voltage
components connected to the
main PCB ( 4-way valve, heater,
AC fan) one by one to check
their resistance. Has any
component short circuit?
No
Unplug the electronic expansion
valve. Check if the power LED is on.