Mitsubishi Electric MXZ-24UV - E1 Service Manual page 28

The cooling operation or heating operation does not operate. (LED display: 0 0 0 0 )
C C Check of R. V. coil
• When heating operation does not work.
Start
1. Disconnect the lead wire leading to the compressor.
2. Turn on power supply to the indoor and outdoor unit, three minutes later
EMERGENCY OPERATION (HEAT operation) starts.
Is there voltage of 230V AC between pin1 and
pin 2 at connector CN913?
Yes
Turn off power supply of indoor and outdoor unit.
Disconnect the connector
CN913 in noise filter P. C.
board, and measure the
resistance of R. V. coil to
check the integrity.
Yes
Replace the 4-way valve
• When cooling operation does not work.
Start
1. Disconnect the lead wire leading to the compressor.
2. Turn on power supply to the indoor and outdoor unit, three minutes later
EMERGENCY OPERATION (COOL operation) starts.
Is there voltage of 230V AC between pin1 and
pin 2 at connector CN913?
Yes
1. Turn off power supply of indoor and outdoor unit, and
disconnect the connector (CN851, CN852) in the electronic
control P. C. board.
2. Turn on power supply to the indoor and outdoor unit, three
minutes later EMERGENCY OPERATION
(COOL operation) starts.
Is there voltage 12V DC between
the connector CN852 pin 1 (+)
and CN851 pin 5 (-)? W1
Yes
Replace the electronic control P. C. board.
No
No
Replace the R. V. coil
No
No
Replace the noise filter P. C. board.
W1 If the connector CN913 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, CN852) in the electronic
control P. C. board.
2. Turn on power supply to the indoor and outdoor unit, three
minutes later EMERGENCY OPERATION
(HEAT operation) starts.
Is there voltage 12V DC between
the connector CN852 pin 1 (+)
and pin 5 (-)?
Yes
Replace the noise filter P. C. board.
Replace the 4-way valve
28
No
Replace the electronic
control P. C. board.