Exhaust Thermistor - A.O. Smith T-H2-DV Service Manual

10-13. Exhaust thermistor

Unit Part #
Function
Failure events
Effects on the water heater
if exhaust thermistor fails
Error codes when exhaust
thermistor fails
Diagnostic
Color/Number of wires
Resistance values of thermistors as a function of temperature
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00
20
#706 Takagi Part #
Measure the exhaust temperatures in the exhaust chamber.
Unable to measure exhaust temperature in the exhaust chamber properly.
If the thermistors fail open or short, error code appears before starting
operation. If resistance values are just off, the "341" error codes will
display.
1. Visual inspection: connection/breakage of wires and/or debris on
impeller.
2. Check voltages: proper range of values shown below.
White - White
Insulating
40 60 80
T-H2-DV/T-H2-OS Service Manual
EKH6E
341 (T-H2-DV only)
68˚F (20°C) 12.6 to 13.4 kΩ
122˚F (50°C) 4.3 to 4.5 kΩ
176˚F (80°C) 1.7 to 1.8 kΩ
(see table below for more resistance values)
Black
100 120 140
Temperature / ºF
32
CONFIDENTIAL
Checkpoint
(Exhaust thermistor) 52
160 180 200
Ver. 1.01
K1
220