Mitsubishi Electric MSZ-EF VE Series Service Manual page 106

MXZ-4D83VA/5D102VA
• When heating operation does not work.
1. Disconnect the lead wire leading to the compressor.
2. 3 minutes after turning ON the breaker, start EMERGENCY
OPERATION in HEAT mode.
Is there voltage of 230 VAC between pin1 and
pin 2 at connector CN912?
Yes
Turn OFF the breaker of the indoor and the 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 breaker, 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 breaker of the indoor and the outdoor
unit, and disconnect the connector CN781.
2. 3 minutes after turning ON the breaker, start
EMERGENCY OPERATION in COOL mode.
Is there voltage 12 VDC
between the connector CN781
pin 5 (+) and pin 3 (-) ?
Yes
Replace the outdoor control P.C. board.
OBH626E
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.
CN721
1. Turn OFF the breaker of the indoor and the outdoor unit, and
disconnect the connector CN781.
2. 3 minutes after turning ON the breaker, 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.
106
MXZ-4D83VA/5D102VA
Outdoor control P.C. board
No
Replace the electronic
control P.C. board.