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