46
G Check of outdoor thermistors
Replace the thermistor except RT64.
When RT64 is abnormal, replace the inverter P.C.
board.
Replace the inverter P.C. board.
No
No
Is the resistance of thermistor normal?
(Refer to 10-6.1.)
Reconnect the connector of thermistor.
Turn ON the power supply and press EMERGENCY OPERATION switch.
Does the unit operate for 10 minutes or more
without showing thermistor abnormality?
OK
(Cause is poor contact.)
Yes
Yes
Disconnect the connector of thermistor in the inverter P.C. board (see
below table), and measure the resistance of thermistor.
Thermistor
Symbol
Connector, Pin No.
Board
Defrost
RT61
Between CN641 pin1 and pin2
Inverter P.C. board
Discharge temperature
RT62
Between CN641 pin3 and pin4
Fin temperature
RT64
Between CN642 pin1 and pin2
Ambient temperature
RT65
Between CN643 pin1 and pin2
Outdoor heat exchanger temperature
RT68
Between CN644 pin1 and pin3
H Check of R.V. coil
First of all, measure the resistance of R.V. coil to check if the coil is defective. Refer to 10-4.
Check if there is 208/230 VAC at L1 - L2.
In case CN721 is disconnected or R.V. coil is open, voltage is generated between the terminal pins of the connector
although no signal is being transmitted to R.V. coil.
Check if CN721 is connected.
Is there 208/230 VAC between CN721
and on the inverter P.C. board
3 minutes after the power supply is turned
ON?
No
Yes
Replace the inverter
P.C. board.
Replace the 4-way valve.
Unit operates COOL mode even if it is set to HEAT mode.
Is there 208/230 VAC between CN721
and on the inverter P.C. board
3 minutes after the power supply is turned
ON?
Yes
No
Replace the inverter
P.C. board.
Replace the 4-way valve.
Unit operates HEAT mode even if it is set to COOL mode.
Disconnect connector between the
compressor and the power module
(IPM) (
MUZ-HM09/12NA(2)
-
U8
)/
(IC700) (
MUZ-HM09/12NA(2)
-
U1
, MUZ-
HM15/18/24NA(2)
).
Turn ON the power supply and press
EMERGENCY OPERATION switch twice
(HEAT mode).
Disconnect connector between the
compressor and the power module
(IPM) (
MUZ-HM09/12NA(2)
-
U8
)/
(IC700) (
MUZ-HM09/12NA(2)
-
U1
, MUZ-
HM15/18/24NA(2)
).
Turn ON the power supply and press
EMERGENCY OPERATION switch once
(COOL mode).
OBH747C