Mitsubishi Electric MXZ-3C24NA Service Manual page 73

• When the operation frequency does not go up from the lowest frequency.
Check of HPS
1. Disconnect the connector CN63H in the outdoor control P.C. board.
2. Check the resistance of HPS after 1 minute has passed since the outdoor unit power supply was turned OFF.
Check the resistance between each terminal.
Reconnect CN63H.
Turn ON the power supply to the indoor and outdoor unit.
3 minutes later, start EMERGENCY OPERATION.
Is HPS protection displayed immediately
after compressor starts?
No
Normal
The other cases
Indoor unit does not operate. (different operating models in multi system)
• When you try to run two indoor units simultaneously, one for cooling and the other for heating, the unit which
transmits signal to the outdoor units first decides the operation mode.
• When the above situation occurs, set all the indoor units to the same mode, turn OFF the indoor units, and
then turn them back ON.
• Though the top of the indoor unit sometimes gets warm, this does not mean malfunction. The reason is that
the refrigerant gas continuously flows into the indoor unit even while it is not operating.
Check of bus-bar voltage
Blink 5 times
Replace the outdoor power
P.C. board.
Turn ON power supply. Start
operation.
Confi rm LED1 indication lamp
on the outdoor control P.C.
board.
Blink 9 times
Replace the outdoor control
P.C. board.
Turn OFF power supply before removing P.C. board.
OBH702A
Infinity
Yes
Replace the outdoor control P.C. board.
•Check the voltage of power supply.
•Confi rm outdoor unit failure mode
recall function. (Refer to 11-2.2.)
Confi rm LED1 indication lamp on the
outdoor control P.C. board.
Normal
Lighting
CN63H
Replace HPS.
Replace the outdoor control
P.C. board.
Turn ON power supply. Start
operation.
Confi rm LED1 indication lamp
on the outdoor control P.C.
Lighting
board.
Replace the outdoor power
P.C. board.
73
Outdoor control
P.C. board
Lighting
Blink 9 times