Mitsubishi Electric MUZ-GE25VA, Service Manual

Page: 49 / 70

49
G Check of outdoor thermistors
H Check of R.V. coil
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
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 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.)
Yes
Yes
Disconnect the connector of thermistor in the outdoor P.C. board (see
below table), and measure the resistance of thermistor.
Thermistor Symbol Connector, Pin No. Board
Defrost RT61 Between CN671 pin1 and pin2
Inverter P.C. board
Discharge temperature RT62 Between CN671 pin3 and pin4
Fin temperature RT64 Between CN673 pin1 and pin2
Ambient temperature RT65 Between CN672 pin1 and pin2
Outdoor heat exchanger temperature RT68 Between CN671 pin5 and pin6
MUZ-GE25VA MUZ-GE35VA MUZ-GE42VA MUZ-GE50VA
MUZ-GE60VA MUZ-GE71VA
First of all, measure the resistance of R.V. coil to check if the coil is defective. Refer to 11-4.
In case CN721 (
MUZ-GE25/35/42/50
)/CN602 (
MUZ-GE60/71
) 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 (
MUZ-GE25/35/42/50
)/CN602 (
MUZ-GE60/71
) is connected.
Is there 230 VAC between CN721 (
MUZ-
GE25/35/42/50
)/CN602 (
MUZ-GE60/71
)
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 230 VAC between CN721 (
MUZ-
GE25/35/42/50
)/CN602 (
MUZ-GE60/71
)
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 intelligent power
module.
Turn ON the power supply and press
EMERGENCY OPERATION switch
twice (HEAT mode).
Disconnect connector between
the compressor and the intelligent
power module.
Turn ON the power supply and
press EMERGENCY OPERATION
switch once (COOL mode).