Mitsubishi Electric MXZ-A14WV Service Manual page 60

The cooling operation or heating operation does not operate. (LED display: Both LED1 and LED2 lighting)
C C Check of R.V. coil
• When heating operation does not work.
Start
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 power supply of indoor and outdoor unit.
Disconnect the connector
CN912 in noise filter P.C.
board. Is there normal
resistance to R.V. coil?
Yes
Replace the 4-way valve.
• When cooling operation does not work.
Start
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 power supply of indoor and outdoor unit, and
disconnect the connector CN851 (MXZ-A14/A18WV)/ CN781
(MXZ-A26/A32WV) in the outdoor electronic control P.C.
board.
2. 3 minutes after turning on the power supply, start
EMERGENCY OPERATION in COOL mode.
Is there voltage 12V DC
between the connector CN851
pin 3 (+) and pin 4 (-) (MXZ-A14/
A18WV)/ CN781 pin 5 (+) and
pin 3 (-) (MXZ-A26/A32WV)? W
Yes
Replace the outdoor electronic control P.C. board.
No
No
Replace the R.V. coil.
No
No
Replace the noise filter P.C. board.
W If the connector CN912 is not connected or R.V. coil is open, voltage
occurs between terminals even when the control is OFF.
1. Turn off power supply of indoor and outdoor unit, and
disconnect the connector CN851 (MXZ-A14/A18WV)/ CN781
(MXZ-A26/A32WV) in the outdoor electronic control P.C.
board.
2. 3 minutes after turning on the power supply, start
EMERGENCY OPERATION in HEAT mode.
Is there voltage 12V DC
between the connector CN851
pin 3 (+) and pin 4 (-) (MXZ-A14/
A18WV)/ CN781 pin 5 (+) and
pin 3 (-) (MXZ-A26/A32WV)?
Yes
Replace the noise filter P.C. board.
Replace the 4-way valve.
60
No
Replace the electronic
control P.C. board.