Navigating the complexities of home appliances can be daunting, especially when they malfunction. AO Smith, a renowned name in water heaters, provides a system of error codes to diagnose issues efficiently. Understanding AO Smith Water Heater Error Codes is crucial for timely troubleshooting and maintaining the longevity of your device.

This guide aims to demystify these codes, offering homeowners clear insights into potential problems and their solutions. Whether you’re a DIY enthusiast or seeking knowledge before consulting a professional, this comprehensive overview will equip you with essential information to manage your AO Smith Water Heater effectively.

Overview of AO Smith Water Heater Error Codes

Error codes in AO Smith Water Heaters serve as essential diagnostic tools, signaling specific issues within the system. These codes appear on the water heater’s display panel, alerting users to a range of problems, from temperature irregularities to sensor malfunctions.

Each code, whether it’s E02 indicating excessively hot water or E51 signifying a control board issue, offers a snapshot of the water heater’s current state.

By understanding these error codes, homeowners can quickly identify the nature of the problem, which is the first step in troubleshooting.

This overview provides a foundational understanding of these error codes, paving the way for more detailed explanations and solutions in subsequent sections of this guide.

AO Smith Water Heater Error Codes

  • Code E02: Indicates overheated water beyond safety limits. Reset the unit after checking for a faulty thermostat or bad computer board​​.
  • Code E03: Low water level, possibly due to air in the waterline or a defective sensor. Clearing the air or replacing the sensor can resolve this issue​​.
  • Code E04: Detects leaks or moisture. Requires identifying and fixing the source of the leak​​.
  • Code E06: Signals excessively high water temperature, often due to a malfunctioning thermostat or heating elements. Adjusting the thermostat and checking heating elements are recommended solutions​​.
  • Codes E10 to E13: Related to open inlet temperature sensors or thermistors. Reconnecting or replacing these components can help​​.
  • Code E14: Specific to 4-chamber models, this code suggests an issue with the outlet thermistor, which may need reconnection or replacement​​.
  • Codes E20 to E24: These codes indicate a short in the thermistor, necessitating its replacement​​.
  • Codes E51 & E52: Signify a loss of connection between the user interface and control board. Replacing the control board is usually required​​.
  • Code ECC: Refers to Electro-chemical compression in heat pump water heaters, highlighting a specific technology used in these models​​.

Guide to AO Smith Water Heater Light Codes

1. No Status Light (Pilot Light Out): Indicates the need to light the pilot. Follow specific instructions for lighting the pilot light​​.

2. Solid Red Light: Signifies the pilot light has recently been extinguished and the thermopile is cooling down. Relight the pilot following given instructions​​.

3. Flashing Light Patterns:

  • 1 Flash Every 3 Seconds: Normal operation, no issues​​.
  • 2 Flashes Every 3 Seconds: Low thermopile voltage, indicating a need to check the thermopile and wiring​​.
  • 4 Flashes Every 3 Seconds: Excessive hot water temperature, suggesting a faulty gas control valve/thermostat which should be replaced​​.
  • 5 Flashes Every 3 Seconds: Defective temperature sensor, requiring replacement​​.
  • 7 Flashes Every 3 Seconds: Faulty gas control valve, which needs replacement​​.
  • 8 Flashes Every 3 Seconds: Gas control valve off but thermopile still generating power, potentially due to a cooling issue or stuck pilot valve. Requires checking and possibly replacing the gas control valve​​.

The light codes offer a quick visual guide to identifying and addressing various conditions of the water heater, enhancing troubleshooting efficiency.


Mastering the AO Smith Water Heater Error and Light Codes is a crucial aspect of managing and maintaining your water heating system. This comprehensive guide provides homeowners and DIY enthusiasts with the insights needed to identify and respond to common issues effectively. Understanding these codes not only facilitates quick troubleshooting but also ensures the longevity and efficient operation of your AO Smith Water Heater. For complex issues, it’s always recommended to consult with certified professionals. A

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