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THERMOSTAT TROUBLESHOOTING FLOW CHART
Check ECO
and ICM
NO
YES
Will ECO board
reset?
YES
High water
temperature
Temp.
0°C 32648 31026 29495
10°C 19898 18968 18088
20°C 12492 11942 11419
30°C
40°C
50°C
60°C
70°C
80°C
90°C
40°F 26109 25400 24712
50°F 19906 19383 18876
70°F 11884 11592 11308
90°F
100°F
120°F
140°F
160°F
180°F
190°F
200°F
FCG3-0805
DCG3 SERIES
No voltage or
low voltage from
thermostat board
& ECO board
With an ohm meter
set at X1, check
NO
orange wires on
set pot. (3,000 ohms
at lowest setting and
0 ohms at highest
Replace
set pot
When slowly turning
set pot dial from low
HAS
to high, ohm reading
BAD SPOT
should be a smooth
transition with no
skips, jumps or
Replace
ECO board
NO
Check orange wire
NO
from ECO board to
Is ECO light on?
damper for 24V
Check
damper
Sensor Resistance vs. Temperature
0
1
2
28049
17253
10922
8057
7722
7403
7099
5327
5117
4917
4726
3602
3468
3340
3217
2488
2400
2316
2235
1752
1693
1637
1582
1256
1216
1177
1140
916
888
861
24045
18383
11032
7333
7165
7000
6839
5827
5697
5570
5446
3758
3679
3602
3527
2488
2439
2391
2344
1688
1656
1625
1595
1170
1150
1129
1110
982
965
949
828
814
801
Copyright© by American Water Heater Company 2005. All rights reserved.
purple wire
between
READING
NO GOOD
setting)
and lowest sensor and
compare reading with
OK
reading from a water
glitches
needed for this test)
OHMS OK
YES
YES
Resistance (K ohms)
3
4
5
6
26682
25389 24166
16461
15710 14998
10450
10000
9572
6808
8532
6268
4543
4368
4201
3099
2986
2878
2157
2083
2011
1530
1480
1432
1105
1070
1037
835
810
786
763
23399
22771 22163
17905
17440 16990
10763
10502 10248
6683
6531
6383
5326
5208
5094
3453
3382
3312
2298
2253
2209
1566
1537
1509
1090
1071
1053
933
917
901
886
788
775
762
749
Replace
bad
sensor(s)
OHMS
Take ohm reading
from upper sensor
chart below.
(A temperature
sample taken from
T&P valve is also
Check purple wire
NO
from thermostat
for 24V
7
8
9
23010 21915
20879
14322 13680
13071
9165
8778
8409
6016
5775
5546
4042
3889
3742
2774
2675
2579
1942
1876
1813
1385
1340
1297
1005
974
944
741
719
698
21573 21000
20445
16553 16128
15715
10000
9760
9526
6238
6098
5961
4982
4873
4767
3244
3177
3112
2166
2124
2083
1481
1454
1427
1035
1017
999
871
857
842
737
725
713
Replace
thermostat
circuit
board
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