Mitsubishi Electric MSZ-FD VA Series Service Manual page 51

O Check of defrost heater
MUZ-FD25VAH MUZ-FD35VAH
Check the following points before checking electric continuity.
1. Does the resistance of ambient temperature thermistor have the characteristics? Refer to 11-6.1.
2. Is the resistance of defrost heater normal? Refer to 11-4.
3. Does the heater protector remain conducted (not open)?
4. Are both ambient temperature thermistor and circuit of defrost heater securely connected to connectors?
In HEAT mode, for more than 5 minutes, let the ambient temperature thermistor continue to read 5°C or
below, and let the defrost thermistor continue to read -1°C or below.
Is there 230 VAC between CN722
the inverter P.C. board? Refer to 11-6.1.
Replace the inverter P.C. board.
P Check of bus-bar voltage
MUZ-FD50
Blink 5 times
Replace the power board.
Turn ON power supply. Start
operation.
Confi rm LED1 indication lamp
on the outdoor electronic con-
trol P.C. board.
Blink 9 times
Replace the outdoor elec-
tronic control P.C. board.
Turn OFF power supply before removing P.C. board.
NOTE: In case both thermistors are more than the above temperature, cool them with cold
water etc...
and on
No
•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 electronic control P.C.
board.
Blink 6 times
Replace the outdoor elec-
tronic control P.C. board.
Normal.
Lighting
Not the problem of the inverter P.C. board.
Yes
Replace the outdoor elec-
tronic control P.C. board.
Turn ON power supply. Start
operation.
Confi rm LED1 indication lamp
on the outdoor electronic con-
Lighting
trol P.C. board.
Replace the power board.
51
Lighting
Blink 9 times