Check Of Outdoor Thermistors; Check Of R.v. Coil - Mitsubishi Electric Mr.Slim MUZ-GC25NA - C1 Service Manual

G Check of outdoor thermistors
Disconnect the connector of thermistor in the outdoor P.C. board (see
below table), and measure the resistance of thermistor.
Is the thermistor normal? (Refer to 9-6.1.
or 9-6.2.)
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.)
MUZ-GC25/35NA MUZ-GC50NA-
Thermistor
Defrost
Discharge temperature
Fin temperature
Ambient temperature (GC50)
Outdoor heat exchanger temperature (GC50)
MUZ-GC50NA- MUZ-GC60/71NA
C1
Thermistor
Defrost
Discharge temperature
Outdoor heat exchanger temperature
Ambient temperature
Fin temperature
H Check of R.V. coil
MUZ-GC25/35NA MUZ-GC50NA-
First of all, measure the resistance of R.V. coil to check if the coil is defective. Refer to 9-4.
In case CN721 is not connected or R.V. coil is open, voltage is generated between the terminal pins of the connector
although any signal is not being transmitted to R.V. coil.
Check if CN721 is connected.
Unit operates COOL mode even if it is set to HEAT mode.
Disconnect connector (CN61)
between the compressor and the
intelligent power module.
Turn ON the power supply and press
EMERGENCY OPERATION switch
twice (HEAT mode).
Unit operates HEAT mode even if it is set to COOL mode.
Disconnect connector (CN61)
between the compressor and the
intelligent power module.
Turn ON the power supply and
press EMERGENCY OPERATION
switch once (COOL mode).
No
Yes
No
Yes
C2
Symbol
RT61 Between CN641 pin1 and pin2
RT62 Between CN641 pin3 and pin4
RT64 Between CN642 pin1 and pin2
RT65 Between CN643 pin1 and pin2
RT68 Between CN644 pin1 and pin3
Symbol
RT61 Between CN661 pin 1 and pin 2
RT62 Between CN661 pin 3 and pin 4
RT68 Between CN661 pin 7 and pin 8
RT65 Between CN663 pin 1 and pin 2
RT64 Between CN3 pin 1 and pin 2
C2
Is there 220 - 230 VAC between CN721
and on the inverter P.C. board 3
minutes after the power supply is turned
ON?
Replace the 4-way valve.
Is there 220 - 230 VAC between CN721
and on the inverter P.C. board 3
minutes after the power supply is turned
ON?
Replace the 4-way valve.
39
Replace the thermistor except RT64.
When RT64 is abnormal, replace the inverter P.C.
board or the outdoor power board.
Replace the inverter P.C. board or the
outdoor electronic control P.C. board.
Connector, Pin No.
Connector, Pin No.
Yes
No
Board
Inverter P.C. board
Board
Outdoor electronic control P.C.
board
Outdoor power board
Replace the inverter
No P.C. board.
Replace the inverter
Yes
P.C. board.