Mitsubishi Electric SUZ-KA09NA2 Service Manual page 21

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 resistance of thermistor normal?
(Refer to "10-6.TEST POINT DIAGRAM AND VOLTAGE".)
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.)
Thermistor
Defrost
Discharge temperature
Fin temperature
Ambient temperature
Outdoor heat exchanger temperature
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. TROUBLE CRITERION OF MAIN
PARTS".
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.
Unit operates in COOL mode even if it is set to HEAT mode.
Disconnect connector between
the compressor and the intelligent
power module.
Turn ON the power supply and
press the TEST button twice (HEAT
mode).
Unit operates in HEAT mode even if it is set to COOL mode.
Disconnect connector between
the compressor and the intelligent
power module.
Turn ON the power supply and
press the TEST button once (COOL
mode).
OCH699A
No
Yes
No
Yes
Symbol Connector, Pin No.
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
Is there 208/230 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 208/230 VAC between CN721
and on the inverter P.C. board 3
minutes after the power supply is turned
ON?
Replace the 4-way valve.
21
Replace the thermistor except RT64. When RT64 is
abnormal, replace the inverter P.C. board.
Replace the inverter P.C. board.
Inverter P.C. board
No
Yes
Yes
No
Board
Replace the inverter
P.C. board.
Replace the inverter
P.C. board.