Mitsubishi Electric MXZ-2B30VA Service Manual page 77

The cooling operation or heating operation does not operate.
Check of R.V. coil
• 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 230V AC 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 230V AC 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 CN933 or CN781.
2. 3 minutes after turning ON the power supply, start
EMERGENCY OPERATION in COOL mode.
Is there voltage 12V DC
between the connector CN933
pin 1 (+) and pin 3 (-) or the
connector CN781 pin 5 (+) and
pin 3 (-) ?
Yes
Replace the inverter P.C. board or outdoor electronic control P.C. board.
OBH554D
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 power P.C. board or
the noise filter P.C. board.
MXZ-2B
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 CN933 or CN781.
2. 3 minutes after turning ON the power supply, start
EMERGENCY OPERATION in HEAT mode.
Is there voltage 12V DC
between the connector CN933
pin 1 (+) and pin 3 (-) or the
connector CN781 pin 5 (+) and
pin 3 (-) ?
Yes
Replace the power P.C. board or
the noise filter P.C. board.
Replace the 4-way valve.
77
MXZ-3B/4B/5B
Noise filter P.C. board
Outdoor electronic control
P.C. board
No
Replace the inverter P.C.
board or the electronic
control P.C. board.