Defective Indoor Unit Heat Exchanger Thermistor; Detective Return Air Thermistor - Mitsubishi Heavy Industries FDCA Series Technical Manual

Error display :
4
Indoor unit
Red LED 1 time flash
Green LED Keeps flashing
Is the indoor
unit heat exchanger
thermistor connector
connection OK?
NO
Correction
● Display condition
If a temperature of –50ºC or lower is detected continuously for 5 seconds or longer by the thermistor, the compres-
sor stops. After a 3 minute delay, the compressor restarts. If this state is detected again within 60 minutes after the
first detection.
Error display :
5
Indoor unit
Red LED 1 time flash
Green LED Keeps flashing
thermistor connector
● Display condition
If a temperature of –50ºC or lower is detected continuously for 5 seconds or longer by the thermistor, the compres-
sor stops. After a 3 minute delay, the compressor restarts. If this state is detected again within 60 minutes after the
first detection.
e6

[Defective indoor unit heat exchanger thermistor]

Red LED
Green LED
Defective indoor unit control PCB
Replace-ment (Defective indoor unit
heat exchanger thermistor input circuit)
YES
exchanger thermistor OK
Defective indoor unit heat exchanger
thermistor
e7

[Detective return air thermistor]

Red LED
Green LED
Is the return air
YES
connection OK?
NO
Correction
Outdoor unit
Stays OFF
Keeps flashing
YES
Are characteristics
of indoor unit heat
or is there any
broken wire?
NO
Replacement
Outdoor unit
Stays OFF
Keeps flashing
Is the return air
thermistor characteristics
OK or is there a
broken wire?
NO
Defective return air
thermistor Replacement
138
- -
Return air thermistor (Th
Indoor unit heat exchanger thermistor
(Th R1, R2)
I-
Resistance temperature characteristics
15
10
5
0 10 20
Temperature (˚C)
Note (1) 22.5 kΩ at -6˚C
Defective indoor unit control PCB
YES
Replacement (Defective return air
thermistor input circuit)
Note (1) Characteristics as per the above
graph.
A)
I-
5kΩ at 25˚C
30 40 50