A.O. Smith 400A - Manual (Page 23)

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• Faults: This is a safety related condition that has been detected by the heater.
NOTE: When these conditions occur, the water heater will not continue any further heating cycles and the water will no longer be
heated until the condition is corrected and, in most cases, power has been cycled.
Example of a Fault:
Advanced Diagnostics Information
When a fault or warning has been declared, advanced information can be found in the control. By pressing the Advanced button,
detailed information can be found regarding diagnosing and resolving the problem.
WARNING: Usage of the Advanced information requires ability equivalent to that of a license tradesmen in the
field involved.
6. Access to the Current Fault or Warning
When a fault or warning has been detected by the control, it will automatically be displayed on the screen and the back light will
blink. If you choose to leave the current fault or warning by pressing the Back key, you can always return to the fault screen through
the menu.