Mitsubishi MUZ-GE25VA Service Manual page 40

Mitsubishi ilmalämpöpumput huoltaa ja korjaa: Jäähdytinpalvelu RefGroup Oy
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 11-6.1.)
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.)
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 11-4.
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 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
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 230 VAC between CN721
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
Replace the 4-way valve.
Is there 230 VAC between CN721
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
Replace the 4-way valve.
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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
and
No
Yes
and
Yes
No
Board
Replace the inverter
P.C. board.
Replace the inverter
P.C. board.