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Service Procedure VII:
Flame Sensor Testing and Replacement
Flame Sensor Replacement Procedure
1. Position main power switch to OFF.
2. Disconnect (unplug) water heater from 120 volt power source.
3. Unlatch and remove surround cover from top of heater.
4. Fold back insulation in front of combustion assembly to expose flame sensor (see image below).
5. Disconnect wire lead from the control board.
6. Remove the 2 sensor mounting screws (magnetic tip, long reach Phillips screwdriver), remove flame sensor,
and gasket from transition base flange.
7. Remove any residual gasket material from transition base flange.
8. Install new flame sensor with new gasket provided using screws from Step 6. Arrange flame sensor with hook
towards burner.
9. Reconnect the flame sensor wire.
10. Fold insulation back into place. Be sure
NO
wires are in contact with burner flange.
11. Restore 120 volt power supply to water heater and confirm proper operation following the lighting instructions on
the lighting instruction label, or the lighting instructions located in the Installation and Operating Manual.
12. Replace the surround cover on the top of the water heater.
Flame Sensor
120T400
120T500
(120T500 model pictured)
WARNING
120 volt potential exposure. Use
caution making voltage checks to
avoid personal injury.
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Summary of Contents for EF120T4003N3
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