Mitsubishi Electric MXZ-2C20NA2 Service Manual page 127

• 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.
0 Ω
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 2 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.
Confirm 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.
OBH702N
Infinity
Replace the outdoor control P.C. board.
Yes
•Check the voltage of power supply.
•Confirm outdoor unit failure mode
recall function. (Refer to 12-2.2.)
Confirm 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.
Confirm LED1 indication lamp
on the outdoor control P.C.
Lighting
board.
Replace the outdoor power
P.C. board. *
127
Outdoor control
P.C. board
Lighting
Blink 9 times