E28 Remote Control Temperature Thermistor Anomaly - Mitsubishi Heavy Industries FDT200VSAPVF1 Service Manual

Error code
E28
Remote control:
1. Applicable model
All models
2. Error detection method
Detection of anomalously low
temperature (resistance) of
remote control 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
control temperature thermistor
• Defective remote control
temperature thermistor
• Defective remote control PCB
Note:
After 10 seconds has passed since remote control 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 control thermistor to indoor return air
temperature thermistor. Even though the remote control thermistor is set to be Effective, the return air temperature displayed on remote control for
checking still shows the value detected by indoor return air temperature thermistor, not by remote control temperature thermistor.
LED Green Red
Keeps flashing Stays OFF
Indoor
Keeps flashing Stays OFF
Outdoor
5. Troubleshooting
Diagnosis
Is the remote
control temperature thermistor
Is the remote
connected properly?
control temperature thermistor
connected properly?
YES
YES
Are the
characteristics of
remote control temperature
thermistor OK?
Are the
Is the thermistor wire
characteristics of
OK?
remote control temperature
thermistor OK?
Is the thermistor wire
OK?
Resistance-temperature characteristics of remote control temperature thermistor (ThC)
Temperature (°C) Resistance value (kΩ)
0 65
1 62
2 59
4 53
6 48
Resistance-temperature characteristics of remote control 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
90
-
Content
Remote control
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
-
'14 • PAC-SM-215
Countermeasure
Correct.
Defective remote control
temperature thermistor ➞
Replace.
Defective remote control
PCB ➞ Replace.
(Defective remote control
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