Mitsubishi Electric MXZ-2A20NA-1 Service Manual page 48

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.
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 208/230V 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?
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 208/230V AC between pin1
and pin 2 at connector CN912? W
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 of 12V DC
between the connector CN781
pin 5 (+) and pin 3 (-) ?
Yes
Replace the outdoor electronic control P.C. board.
No
No
Replace the R.V. coil.
No
W 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.
CN912
CN781
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 of 12V DC
between 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.
48
Noise filter P.C. board
Outdoor electronic control
P.C. board
No
Replace the outdoor
electronic control P.C.
board.