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240 (T-H3J), 340 (T-H3S) and 540 (T-H3) models Service Manial
Ver. 1.00
CONFIDENTIAL
10-13. Exhaust thermistor
Part# • 319143-131 (EKH6E) Unit Part# #718
Function Measures the exhaust temperatures in the secondary heat exchanger.
Failure events Unable to measure exhaust temperature in the exhaust chamber properly.
Effects on the water heater
if exhaust thermistor fails
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.
Error codes when exhaust
thermistor fails
341 (Direct Vent Indoor models only)
Diagnostic
1. Visual inspection: connection/breakage of wires and/or debris on
impeller.
2. Check voltages: proper range of values shown below.
Color / Number of wires White - White
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)
Check
point
K1
Resistance values of thermistors as a function of temperature
Black
(Exhaust thermistor)
Insulation
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