57
Procedure for Checking Thermostat Sensors
Set the thermostat above water temperature (See temperature adjustment section) and observe system through one (1)
complete cycle. Make sure system operates as desired.
To check the upper sensor assembly, compare the resistance of the sensor terminals (yellow and black lead for upper
sensor) as measured by an ohmmeter to the water temperature as measured by an accurate thermometer. Thermistor
resistance increases as the temperature decreases. The tables below show the correct sensor resistance at various
temperatures. Replace the sensor if the ohm reading in the chart does not approximate the reading from the sensor at the
temperature measured in the tank.
In Degrees F
°F
0
1
2
3
4
5
6
7
8
9
40
26109
25400 24712
24045
23399 22771
22163
21573 21000
20445
50
19906
19383 18876
18383
17905 17440
16990
16553 16128
15715
60
15314
14925 14548
14180
13823 13477
13140
12812 12494
12185
70
11884
11592 11308
11032
10763 10502
10248
10000
9760
9526
80
9299
9078
8862
8653
8449
8250
8057
7869
7685
7507
90
7333
7165
7000
6839
6683
6531
6383
6238
6098
5961
100
5827
5697
5570
5446
5326
5208
5094
4982
4873
4767
110
4663
4562
4464
4368
4274
4183
4094
4006
3922
3839
120
3758
3679
3602
3527
3453
3382
3312
3244
3177
3112
130
3048
2986
2925
2866
2808
2752
3697
3643
2590
2538
140
2488
2439
2391
2344
2298
2253
2209
2166
2124
2083
150
2043
2004
1966
1928
1891
1856
1820
1786
1753
1720
160
1688
1656
1625
1595
1566
1567
1509
1481
1454
1427
170
1402
1376
1351
1327
1303
1280
1257
1235
1213
1191
180
1170
1150
1129
1110
1090
1071
1053
1035
1017
999
190
982
965
949
933
917
901
886
871
857
842
200
828
814
801
788
775
762
749
737
725
713
In Degrees C
°C
0
1
2
3
4
5
6
7
8
9
0
32648 31026 29495 28049 26682 25389 24166 23010 21915 20879
10
19898 18968 18088 17253 16461 15710 14998 14322 13680 13071
20
12492 11942 11419 10922 10450 10000
9572
9165
8778
8409
30
8057
7722
7403
7099
6808
8532
6268
6016
5775
5546
40
5327
5117
4917
4726
4543
4368
4201
4042
3889
3742
50
3602
3468
3340
3217
3099
2986
2878
2774
2675
2579
60
2488
2400
2316
2235
2157
2083
2011
1942
1876
1813
70
1752
1693
1637
1582
1530
1480
1432
1385
1340
1297
80
1256
1216
1177
1140
1105
1070
1037
1005
974
944
90
916
888
861
835
810
786
763
741
719
698