8
Thermistor Field Testing
Use the guide below to test if a thermistor (temperature probe) is functioning properly. See the replacement parts list for
part number information. Table 2 is valid for all thermistors listed on table 1.
•
Establish Thermistor Temperature
▪
Check the display’s temperature reading.
▪
If a thermometer is available, use it to confirm the display’s
temperature reading by taking the temperature at the
thermistor.
▪
If the previously stated tasks are unavailable, then use any
reasonable means to estimate the thermistors temperature.
See form M164 for ice bath method. (ice water is 32
°
F)
•
Multimeter Set-up
▪
Use a multimeter and set it to the resistance (Ω) setting. See
Figure 1.
▪
Disconnect the thermistor from the controller, then connect the
multimeter to the thermistor. See Figure 1.
▪
Check and compare the multimeter’s reading to Table 1.
•
Analyze Results
▪
If the resistance and temperature are similar, then the
thermistor is working properly and does not need to be
replaced.
▪
If the resistance and temperature are not similar or the
resistance’s value is not on Table 1, then the thermistor is not
working properly and needs to be replaced.
▪
If the resistance reads over-limit, then the thermistor is not
working properly and needs to be replaced.
Figure 1
Table 1
Thermistor Description
Part Number
60” black
120” black
60” green
120” green
96” black
Table 2
Temp
(
°
F)
Ohms
(kΩ)
Temp
(
°
C)
-4.0
67.8
-20
-0.4
61.5
-18
3.2
56.0
-16
6.8
51.0
-14
10.4
46.5
-12
14.0
42.5
-10
17.6
38.8
-8
21.2
35.4
-6
24.8
32.4
-4
28.4
29.7
-2
32.0
27.3
0
35.6
25.0
2
39.2
23.0
4
42.8
21.2
6
46.4
19.5
8
50.0
18.0
10
53.6
16.6
12
57.2
15.3
14
60.8
14.1
16
64.4
13.0
18
68.0
12.1
20
71.6
11.2
22
75.2
10.4
24
78.8
9.6
26
82.4
8.9
28
86.0
8.3
30
89.6
7.7
32
93.2
7.2
34
96.8
6.7
36
100.4
6.3
38
104
5.8
40
P/N 45810 - Rev C
