Remote Controller Temperature Thermistor Anomaly (Thc) - Mitsubishi Heavy Industries KX6 series Service Manual

Error code
E28
Remote controller:
-
7-segment display:
1. Applicable model
All models
2. Error detection method
Detection of anomalously low
temperature (resistance)
of Thc
3. Condition of error displayed
• If -50ºC or lower is detected
for 5 seconds continuously,
compressor stops. After
3-minutes delay, the
compressor is restarted
automatically, biut if this
anomaly occurs again within
60 minutes after the initial
detection.
4. Presumable cause
• Anomalous connection of
remote controller temperature
thermistor
• Remote controller temperature
thermistor anomaly
• Remote controller PCB
anomaly
Note:
After 10 seconds has elapsed since remote controller temperature thermistor was switched from invalid to valid, E28 will not be displayed
even if the thermistor harness is disconnected or broken. However, in such case, the indoor return air temperature thermistor (Thi-A) will
be valid instantly instead of the remote controller temperature thermistor (Thc).
Please note that even though the remote controller temperature thermistor (Thc) is valid, the displayed return air temperature on the
remote controller LCD shows the value detected by the indoor return air temperature thermistor (Thi-A), not by the remote controller
temperature thermistor (Thc).
LED Green Red
Keeps flashing Stays Off
Indoor
Keeps flashing Stays Off
Outdoor
5. Troubleshooting
Diagnosis
Is
the connector of
thermistor connected
properly ?
YES
Regarding the characteristics of the thermistor,
see the following table
Are
the characteristics
of thermistor OK?
Is the thermistor wire
OK *1
*1 Check several times to prove any poor connection
Temperature-resistance characreristics of remote
controller temperature thermistor (Thc)
Temperature (°C) Resistance (kΩ) Temperature (°C) Resistance (kΩ) Temperature (°C) Resistance (kΩ) Temperature (°C) Resistance (kΩ)
0 65 14 33
1 62 16 30
2 59 18 27
4 53 20 25
6 48 22 23
8 44 24 21
10 40 26 19
12 36 28 18
73
–
Content
Remote controller
temperature thermistor anomaly (Thc)
NO
NO
YES
30 16 46 8.5
32 15 48 7.8
34 14 50 7.3
36 13 52 6.7
38 12 54 6.3
40 11 56 5.8
42 9.9 58 5.4
44 9.2 60 5.0
–
'10 • KX-SM-148
Countermeasure
Insert the connector
securely
Replace thermistor
(Thc)
Replace indoor control
PCB