Mitsubishi Heavy Industries FDT100VNAWVH Service Manual page 156

Error code
E28
Remote control:
1. Applicable model
All models
2. Error detection method
Detection of anomalously low
temperature (resistance) of
remote control temperature
sensor (Thc)
3. Condition of error displayed
When the temperature sensor
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 sensor
• Defective remote control
temperature sensor
• Defective remote control PCB
Note:
After 10 seconds has passed since remote control sensor was switched from valid to invalid, E28 will not be displayed even if the sensor harness is
disconnected. At same time the sensor, which is effective, is switched from remote control temperature sensor to indoor return air temperature sensor.
Even though the remote control temperature sensor 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 sensor, not by remote control temperature sensor.
RUN light TIMER light
Indoor
display
– –
Green LED Red LED
Outdoor unit
control PCB
Keeps flashing Stays OFF
5. Troubleshooting
Diagnosis
Is the remote
control temperature sensor
connected properly?
YES
Are the
characteristics of
remote control temperature
sensor OK?
Is the remote
Is the sensor wire
control temperature sensor
OK?
connected properly?
YES
Are the
Resistance-temperature characteristics of remote control temperature sensor (Thc)
characteristics of
Temperature (°C) Resistance value (k )
remote control temperature
0 65
sensor OK?
1 62
2 Is the sensor wire 59
4 53
OK?
6 48
8 44
10 40
12 36
14 33
16 30
18 27
20 25
22 23
24 21
Resistance-temperature characteristics of remote control temperature sensor (Thc)
26 19
28 18
Temperature (°C) Resistance value (k )
0
1
2
4
6
8
10
12
14
16
18
20
22
24
26
28
155
-
Content
Remote control
temperature sensor anomaly
NO
NO
NO
YES
Temperature (°C) Resistance value (k )
30
NO
32
34
36
38
40
42
44
46
YES
48
50
52
54
56
58
60
Temperature (°C)
65 30
62 32
59 34
53 36
48 38
44 40
40 42
36 44
33 46
30 48
27 50
25 52
23 54
21 56
19 58
18 60
-
'19 • PAC-SM-309
Countermeasure
Correct.
Defective remote control
temperature sensor ➞
Replace.
Defective remote control
PCB ➞ Replace.
(Defective remote control
temperature sensor input
circuit)
16
15
14
13
12
11
9.9
9.2
8.5
7.8
7.3
6.7
6.3
5.8
5.4
5.0
Resistance value (k )
16
15
14
13
12
11
9.9
9.2
8.5
7.8
7.3
6.7
6.3
5.8
5.4
5.0