Carrier 40MBFAQ Service Manual page 16

40MBFAQ: Service Manual
DIAGNOSIS AND SOLUTION (CONT.)
EL 01 (Indoor and Outdoor Unit Communication Error Diagnosis and Solution)
Description: Indoor unit cannot communicate with the outdoor unit
Recommended parts to prepare:
• Indoor PCB
• Outdoor PCB
• Reactor
Troubleshooting
Power off , then restart the unit after 2
minutes.
Does the error code disappear?
Check the
wiring connection
between the indoor and outdoor
unit. Are they good?
Measure the DC voltage between N/L2
and S (Black pin to N/L2, Red pin to S).
For units with a 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 the
main PCB such as 4-way valve, heater,
and AC fan (one by one) to check
their resistance. Has any component
Check the DC 5V, 12V
from IPM board to main
PCB. Are they normal?
Unplug electronic expansion valve.
Check if the DC, 5V, 12V to main
PCB are in working order.
Replace the IPM board.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
No
Yes
Correct the connection or
No
change wires.
The value alternates from
negative to positive.
Yes
The value is fixed and close
The value is always positive.
For units without W
wire
If there is more than 1 PCB,
check the wiring connection
(both)
from the outdoor terminal to
the outdoor PCB and the
wiring between PCBs.
Replace the
No
main PCB.
Yes
Yes
short-circuited?
Yes
No
No
Yes
No
Solved
Check the wiring connection
from the indoor terminal to the
to 0.
indoor PCB. Are they good?
For units with
a W wire
Turn on the unit, check if W
and 1 (L) are connected.
Yes
For units with only one PCB.
Replace the outdoor PCB.
Replace the short-circuited
component and the
main PCB.
Replace the short-circuited
Yes
component and the
outdoor PCB.
No
Replace the electronic
Yes
expansion valve coil.
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
16
Replace indoor PCB.
No
Yes Check if the power LED is on.
No
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?
No
Unplug electronic expansion valve.
Check if power LED is on.
whole.