Mitsubishi Electric MXZ-2C30VA Service Manual page 102

The cooling operation or heating operation does not operate.
Check of R.V. coil
MXZ-2C30/2C40/2C52/3C54/3C68/4C71/4C80/5C100VA
MXZ-4C80/5C100VA2
• When heating operation does not work.
1. Disconnect the lead wire leading to the compressor.
2. 3 minutes after turning ON the power supply, start EMERGENCY
OPERATION in HEAT mode.
Is there voltage of 230 VAC between pin1 and
pin 2 at connector CN912?
Yes
Turn OFF the power supply of indoor and outdoor unit.
Disconnect the connector
CN912. Is there normal
resistance to R.V. coil?
(Refer to 11-5.)
Yes
Replace the 4-way valve.
• When cooling operation does not work.
1. Disconnect the lead wire leading to the compressor.
2. 3 minutes after turning ON the power supply, start EMERGENCY
OPERATION in COOL mode.
Is there voltage of 230 VAC between pin1 and
pin 2 at connector CN912?
Yes
1. Turn OFF the power supply of the indoor and the outdoor
unit, and disconnect the connector CN781.
2. 3 minutes after turning ON the power supply, start
EMERGENCY OPERATION in COOL mode.
Is there voltage 12 VDC
between the connector CN781
pin 5 (+) and pin 3 (-) ?
Yes
Replace the electronic control P.C. board.
OBH584G
No
No
Replace the R.V. coil.
No
If the connector CN912 is not connected or R.V. coil is open, voltage
occurs between terminals even when the control is OFF.
No
Replace the noise filter P.C. board.
MXZ-2C
CN912 Power P.C. board
CN781
CN933 Inverter P.C. board
1. Turn OFF the power supply of indoor and outdoor unit, and
disconnect the connector CN781.
2. 3 minutes after turning ON the power supply, start
EMERGENCY OPERATION in HEAT mode.
Is there voltage 12 VDC
between the connector
CN781 pin 5 (+) and pin 3 (-) ?
Yes
Replace the noise filter P.C. board.
Replace the 4-way valve.
102
MXZ-3C/4C/5C
Noise filter P.C. board
Electronic control P.C.
board
No
Replace the electronic
control P.C. board.