Mitsubishi Electric Mr. SLIM PCA-M71HA2 Service Manual page 18

Phenomena
(2) LED2 on indoor controller board
is blinking.
9-5. WHEN WIRED REMOTE CONTROLLER OR INDOOR UNIT MICROPROCESSOR FAILS
1. When the wired remote controller or the indoor unit microprocessor has failed, but all other components work properly,
if you set the switch (SWE) on the indoor controller board ON, the indoor unit will start emergency operation.
When emergency operation is activated, the indoor unit operates as follows:
• Indoor fan runs at high speed.
2. When you activate emergency operation of the cooling or heating, you have to set the switch (SWE) on the indoor controller
board and activate emergency operation of the outdoor unit.
For details on how to activate emergency operation of the outdoor unit, refer to the outdoor unit wiring diagram.
3. Before you activate emergency operation, check the following points:
(1) Emergency operation cannot be activated when:
• the outdoor unit malfunctions. • the indoor fan malfunctions.
(2) Emergency operation becomes continuous only by switching the power source on/off.
ON/OFF on the remote control or temperature control, etc. does not function.
(3) Avoid operating for a long time when the outdoor unit starts defrosting while emergency operation of the heating is activat-
ed because it will start to blow cold air.
(4) Emergency cooling should be limited to 10 hours maximum (The indoor unit heat exchanger may freeze).
(5) After emergency operation has been deactivated, set the switches, etc. to their original positions.
OCH753A
Note: Refer to the outdoor unit's service manual for the detail of remote controller.
Cause
• When LED1 on indoor controller board is also blinking.
Connection failure of indoor/outdoor unit connecting
wire
• When LED1 is lit
Miswiring of remote controller wires
Under twin triple indoor unit system, 2 or more indoor
units are wired together.
Refrigerant address for outdoor unit is wrong or not
set.
Under grouping control system, there are some units
whose refrigerant address is 0.
Short-cut of remote controller wires
Defective remote controller
Check indoor/outdoor unit connecting
wire for connection failure.
Check the connection of remote controller
wires in the case of twin triple indoor unit
system. When 2 or more indoor units are
wired in one refrigerant system, connect
remote controller wires to one of those units.
Check the setting of refrigerant address
in the case of grouping control system.
If there are some units whose refrigerant
address is 0 in one group, set one of the
units to 0 using SW1 (3-6) on outdoor
controller circuit board.
Remove remote controller wires and
check LED2 on indoor controller board.
• When LED2 is blinking, check the
short-cut of remote controller wires.
• When LED2 is lit, connect remote
controller wires again and:
if LED2 is blinking, remote controller
is defective; if LED2 is lit, connection
failure of remote controller terminal
block etc. has returned to normal.
18
Countermeasure