Mitsubishi Heavy Industries FDT40VF Technical Manual page 448

Error code
Remote controller: E28
1. Applicable model
All models
2. Error detection method
Detection of anomalously low
temperature (resistance) of
remote controller temperature
thermistor (Thc)
3. Condition of Error displayed
When the temperature
thermistor detects -50°C
or lower for 5 seconds
continuously, the compressor
stops. After 3-minutes delay,
the compressor starts again
automatically, but if this error
occurs again within 60 minutes
after the initial detection.
4. Presumable cause
• Faulty connection of remote
controller temperature
thermistor
• Defective remote controller
temperature thermistor
• Defective remote controller
PCB
Note:
After 10 seconds has passed since remote controller thermistor was switched from valid to invalid, E28 will not be displayed even if the
thermistor harness is disconnected. At same time the thermistor, which is effective, is switched from remote controller thermistor to indoor return
air temperature thermistor. Even though the remote controller thermistor is set to be Effective, the return air temperature displayed on remote
controller for checking still shows the value detected by indoor return air temperature thermistor, not by remote controller temperature thermistor.
RUN light TIMER light
Indoor
display
– –
Green LED Red LED
Outdoor
control PCB
Keeps flashing Stays OFF
5. Troubleshooting
Diagnosis
Is the remote
controller temperature thermistor
Is the remote
connected properly?
controller temperature thermistor
connected properly?
YES
YES
Are the
characteristics of
remote controller temperature
thermistor OK?
Are the
Is the thermistor wire
characteristics of
OK?
remote controller temperature
thermistor OK?
Is the thermistor wire
OK?
Resistance-temperature characteristics of remote controller temperature thermistor (ThC)
Temperature (°C) Resistance value (kΩ)
0 65
1 62
2 59
4 53
6 48
Resistance-temperature characteristics of remote controller temperature thermistor (ThC)
8 44
Temperature (°C) Resistance value (kΩ)
10 40
0
12 36
14 33
1
16 30
2
18 27
4
20 25
6
22 23
24 21
8
26 19
10
28 18
12
14
16
18
20
22
24
26
28
448 448
- -
Content
Remote controller
temperature thermistor anomaly
NO
NO
NO
NO
YES
YES
Temperature (°C) Resistance value (kΩ)
30
32
34
36
38
40
Temperature (°C)
42
65 30
44
46
62 32
48
59 34
50
53 36
52
48 38
54
56
44 40
58
40 42
60
36 44
33 46
30 48
27 50
25 52
23 54
21 56
19 58
18 60
- -
'12 • PAC-T-173
Countermeasure
Correct.
Defective remote controller
temperature thermistor ➞
Replace.
Defective remote controller
PCB ➞ Replace.
(Defective remote
controller temperature
thermistor input circuit)
16
15
14
13
12
11
Resistance value (kΩ)
9.9
16
9.2
8.5
15
7.8
14
7.3
13
6.7
12
6.3
5.8
11
5.4
9.9
5.0
9.2
8.5
7.8
7.3
6.7
6.3
5.8
5.4
5.0