Mitsubishi Electric MUZ-LN25VG Service Manual page 44

H Check of R.V. coil
MUZ-LN25/35/50VG
First of all, measure the resistance of R.V. coil to check if the coil is defective. Refer to 12-4.
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 between the
compressor and the IGBT module
(IC700).
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 between the
compressor and the IGBT module
(IC700).
Turn ON the power supply and
press EMERGENCY OPERATION
switch once (COOL mode).
MUZ-LN60VG
First of all, measure the resistance of R.V. coil to check if the coil is defective. Refer to 11-4.
In case CN602 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 CN602 is connected.
Unit operates COOL mode even if it is set to HEAT mode.
Disconnect connector between the
compressor and the power module
(IC700).
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 between the
compressor and the power module
(IC700).
Turn ON the power supply and
press EMERGENCY OPERATION
switch once (COOL mode).
OBH767
Is there 230 V AC between CN721
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
Yes
Replace the 4-way valve.
Is there 230 V AC between CN721
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
No
Replace the 4-way valve.
Is there 230 V AC between CN602
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
Yes
Replace the 4-way valve.
Is there 230 V AC between CN602
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
No
Replace the 4-way valve.
44
and
Replace the inverter
No P.C. board.
and
Replace the inverter
Yes
P.C. board.
and
Replace the inverter
No P.C. board.
and
Replace the inverter
Yes
P.C. board.