Mitsubishi Electric MXZ-4E72VA-E1 Service Manual page 105

The cooling operation or heating operation does not operate.
Check of R.V. coil
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 220-230-240 V AC between
pin1 and pin2 at connector CN712?
Yes
Turn OFF the power supply.
Disconnect the connector CNAC2.
Is there normal resistance
to R.V. coil? (Refer to 11-5.)
Yes
Replace the 4-way valve.
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 220-230-240 V AC between
pin1 and pin2 at connector CN712?
Yes
Replace the outdoor control P.C. board.
OBH723G
No
No
Replace the R.V. coil.
No
Is there voltage 220-230-240 V AC
between the pin1 and pin3 at
connector CNAC?
Yes
Replace the outdoor
control P.C. board.
Replace the 4-way valve.
105
CNAC Outdoor control
CN712 P.C. board
Outdoor power
CNAC2
P.C. board
No Replace the outdoor
power P.C. board.