Heating - Mitsubishi Electric MXZ-18TV Service Manual

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 CN912?
Yes
Turn off power supply of indoor and outdoor unit.
Disconnect the connector
CN912 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 CN912?
Yes
1. Turn off power supply of indoor and outdoor unit, and
disconnect the connector (CN851) in the outdoor 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 CN851 pin 3 (+)
and pin 4 (-)? W1
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.
W1 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) in the outdoor 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 CN851 pin 3 (+)
and pin 4 (-)?
Yes
Replace the noise filter P. C. board.
Replace the 4-way valve
23
No
Replace the electronic
control P. C. board.