A.O. Smith Water Heaters Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E01
Electronic gas water heater will not ignite; display shows E01 and burner never lights
Ignition Failure Lockout
E02
Gas water heater attempts to light but shuts down; display shows E02
Flame Loss / Flame Sense Failure
E03
A.O. Smith gas water heater shows E03 and shuts down shortly after ignition attempt
Pressure Switch or Combustion Air Proving Failure (Power Vent / Direct Vent Models)
E04
Power vent A.O. Smith water heater shows E04 and will not fire
Blower / Draft Inducer Failure
E05
A.O. Smith gas water heater displays E05 and shuts down; unit may overheat or cycle rapidly
High Limit / ECO (Energy Cut-Off) Trip
E06
A.O. Smith tankless or high-efficiency water heater shows E06 and stops heating
Outlet Temperature Sensor Failure
E07
A.O. Smith water heater shows E07; unit may shut down or run erratically
Inlet Temperature Sensor Failure
E08
A.O. Smith tankless or high-efficiency heater shows E08 and stops heating
Heat Exchanger Overheat / Outlet Over-Temperature
E09
A.O. Smith water heater displays E09 and will not operate.
Exhaust Temperature Sensor / Flue Sensor Fault
E10
A.O. Smith water heater displays E10; the unit may not respond to controls.
Communication Error Between User Interface and Control Board
E11
A.O. Smith tankless or condensing heater displays E11 and shuts down.
Gas Valve / Gas Control Fault
E12
A.O. Smith water heater displays E12; the unit may lock out after several failed starts.
Flame Rod Short / Ground Fault
E13
A.O. Smith heater displays E13 and will not start; often associated with condensate issues on condensing models.
Condensate Drain / Float Switch Fault
E14
A.O. Smith water heater displays E14; the unit may not respond to thermostat changes.
Thermostat / Setpoint Sensor Fault
E15
A.O. Smith heater displays E15; the unit may shut down unexpectedly.
Flame Rollout Switch / Manual Reset Limit Open
E16
A.O. Smith water heater displays E16; the unit may not heat or may cycle rapidly.
Recirculation Pump Fault (Models with Built-In Pump)
E17
A.O. Smith heater displays E17; the unit may not modulate correctly or may shut down.
Fan Speed / Combustion Air Fault
E18
A.O. Smith water heater displays E18; the unit may not start or may shut down intermittently.
Line Voltage / Power Supply Fault
E19
A.O. Smith heater shows E19; the unit may not recognize sensors or accessories.
Accessory / Sensor Bus Communication Fault
E20
A.O. Smith electric water heater shows E20 and does not heat properly.
Upper Element / Thermostat Circuit Fault
E21
A.O. Smith electric water heater shows E21; the lower portion of the tank stays cold.
Lower Element / Thermostat Circuit Fault
E22
A.O. Smith electric water heater shows E22; water temperature is erratic.
Thermostat Calibration / Sensor Error
E23
A.O. Smith hybrid heat pump water heater shows E23 and may revert to electric-only mode.
Evaporator Coil / Refrigerant System Fault
E24
A.O. Smith hybrid water heater shows E24; the fan may not run.
Heat Pump Fan Motor Fault
E25
A.O. Smith hybrid water heater shows E25; the unit may shut down heat pump operation.
Condensate Pan Full / Condensate Pump Fault (Hybrid Models)
Symptom
A.O. Smith gas water heater pilot light will not stay lit.
Pilot Safety Circuit Failure
Symptom
A.O. Smith hybrid heat pump water heater not producing sufficient hot water in heat pump mode.
Insufficient Heat Pump Capacity or Control Setting
Symptom
A.O. Smith tankless water heater cycles on and off during use, causing temperature swings.
Flow Modulation / Minimum Flow Issue
Symptom
A.O. Smith water heater status light blinking, but no hot water (lockout condition on FVIR models).
Flammable Vapor Ignition Resistance (FVIR) System Lockout
Symptom
A.O. Smith water heater trips the electrical breaker repeatedly.
Electrical Overload or Short Circuit
Symptom
An A.O. Smith water heater emits a rotten egg or sulfur smell from hot water taps.
Hydrogen Sulfide Odor Reaction
Symptom
An A.O. Smith water heater has discolored or rusty hot water.
Internal Corrosion or Rust Contamination
Symptom
An A.O. Smith water heater makes a high-pitched whistling or screeching noise when running.
Flow Restriction or Partially Closed Valve
Symptom
An A.O. Smith water heater makes popping or rumbling noises during heating.
Sediment Boiling / Kettling
Symptom
An A.O. Smith water heater vibrates or makes banging noises in the piping when heating.
Water Hammer or Thermal Expansion Noise
Symptom
Condensation or water pooling around the base of an A.O. Smith gas water heater shortly after installation.
Normal Condensation or Minor Leak
Symptom
Hot water runs out quickly from an A.O. Smith tank-type water heater.
Reduced Effective Capacity / Stratification Issue
Symptom
No hot water at all from A.O. Smith gas water heater (no error code on basic models).
Complete Ignition or Gas Supply Failure
Symptom
No hot water from A.O. Smith electric water heater (no digital display).
Power Loss or Dual Element Circuit Failure
Symptom
Water heater leaking from the bottom of the tank.
Tank Corrosion / Internal Tank Failure
Symptom
Water is warm but not hot enough from A.O. Smith gas water heater.
Insufficient Burner Operation or Thermostat Misadjustment
Symptom
Water is warm but not hot enough from an A.O. Smith electric water heater.
Single Element Operation or Thermostat Misadjustment
Symptom
Water leaking from the temperature and pressure (T&P) relief valve on an A.O. Smith water heater.
Over-Pressure or Over-Temperature Relief Discharge
Symptom
Water leaking from the top of an A.O. Smith water heater around the piping.
Connection or Fitting Leak
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E01 |
Electronic gas water heater will not ignite; display shows E01 and burner never lights
|
Ignition Failure Lockout | View Details |
| E02 |
Gas water heater attempts to light but shuts down; display shows E02
|
Flame Loss / Flame Sense Failure | View Details |
| E03 |
A.O. Smith gas water heater shows E03 and shuts down shortly after ignition attempt
|
Pressure Switch or Combustion Air Proving Failure (Power Vent / Direct Vent Models) | View Details |
| E04 |
Power vent A.O. Smith water heater shows E04 and will not fire
|
Blower / Draft Inducer Failure | View Details |
| E05 |
A.O. Smith gas water heater displays E05 and shuts down; unit may overheat or cycle rapidly
|
High Limit / ECO (Energy Cut-Off) Trip | View Details |
| E06 |
A.O. Smith tankless or high-efficiency water heater shows E06 and stops heating
|
Outlet Temperature Sensor Failure | View Details |
| E07 |
A.O. Smith water heater shows E07; unit may shut down or run erratically
|
Inlet Temperature Sensor Failure | View Details |
| E08 |
A.O. Smith tankless or high-efficiency heater shows E08 and stops heating
|
Heat Exchanger Overheat / Outlet Over-Temperature | View Details |
| E09 |
A.O. Smith water heater displays E09 and will not operate.
|
Exhaust Temperature Sensor / Flue Sensor Fault | View Details |
| E10 |
A.O. Smith water heater displays E10; the unit may not respond to controls.
|
Communication Error Between User Interface and Control Board | View Details |
| E11 |
A.O. Smith tankless or condensing heater displays E11 and shuts down.
|
Gas Valve / Gas Control Fault | View Details |
| E12 |
A.O. Smith water heater displays E12; the unit may lock out after several failed starts.
|
Flame Rod Short / Ground Fault | View Details |
| E13 |
A.O. Smith heater displays E13 and will not start; often associated with condensate issues on condensing models.
|
Condensate Drain / Float Switch Fault | View Details |
| E14 |
A.O. Smith water heater displays E14; the unit may not respond to thermostat changes.
|
Thermostat / Setpoint Sensor Fault | View Details |
| E15 |
A.O. Smith heater displays E15; the unit may shut down unexpectedly.
|
Flame Rollout Switch / Manual Reset Limit Open | View Details |
| E16 |
A.O. Smith water heater displays E16; the unit may not heat or may cycle rapidly.
|
Recirculation Pump Fault (Models with Built-In Pump) | View Details |
| E17 |
A.O. Smith heater displays E17; the unit may not modulate correctly or may shut down.
|
Fan Speed / Combustion Air Fault | View Details |
| E18 |
A.O. Smith water heater displays E18; the unit may not start or may shut down intermittently.
|
Line Voltage / Power Supply Fault | View Details |
| E19 |
A.O. Smith heater shows E19; the unit may not recognize sensors or accessories.
|
Accessory / Sensor Bus Communication Fault | View Details |
| E20 |
A.O. Smith electric water heater shows E20 and does not heat properly.
|
Upper Element / Thermostat Circuit Fault | View Details |
| E21 |
A.O. Smith electric water heater shows E21; the lower portion of the tank stays cold.
|
Lower Element / Thermostat Circuit Fault | View Details |
| E22 |
A.O. Smith electric water heater shows E22; water temperature is erratic.
|
Thermostat Calibration / Sensor Error | View Details |
| E23 |
A.O. Smith hybrid heat pump water heater shows E23 and may revert to electric-only mode.
|
Evaporator Coil / Refrigerant System Fault | View Details |
| E24 |
A.O. Smith hybrid water heater shows E24; the fan may not run.
|
Heat Pump Fan Motor Fault | View Details |
| E25 |
A.O. Smith hybrid water heater shows E25; the unit may shut down heat pump operation.
|
Condensate Pan Full / Condensate Pump Fault (Hybrid Models) | View Details |
| – |
A.O. Smith gas water heater pilot light will not stay lit.
|
Pilot Safety Circuit Failure | View Details |
| – |
A.O. Smith hybrid heat pump water heater not producing sufficient hot water in heat pump mode.
|
Insufficient Heat Pump Capacity or Control Setting | View Details |
| – |
A.O. Smith tankless water heater cycles on and off during use, causing temperature swings.
|
Flow Modulation / Minimum Flow Issue | View Details |
| – |
A.O. Smith water heater status light blinking, but no hot water (lockout condition on FVIR models).
|
Flammable Vapor Ignition Resistance (FVIR) System Lockout | View Details |
| – |
A.O. Smith water heater trips the electrical breaker repeatedly.
|
Electrical Overload or Short Circuit | View Details |
| – |
An A.O. Smith water heater emits a rotten egg or sulfur smell from hot water taps.
|
Hydrogen Sulfide Odor Reaction | View Details |
| – |
An A.O. Smith water heater has discolored or rusty hot water.
|
Internal Corrosion or Rust Contamination | View Details |
| – |
An A.O. Smith water heater makes a high-pitched whistling or screeching noise when running.
|
Flow Restriction or Partially Closed Valve | View Details |
| – |
An A.O. Smith water heater makes popping or rumbling noises during heating.
|
Sediment Boiling / Kettling | View Details |
| – |
An A.O. Smith water heater vibrates or makes banging noises in the piping when heating.
|
Water Hammer or Thermal Expansion Noise | View Details |
| – |
Condensation or water pooling around the base of an A.O. Smith gas water heater shortly after installation.
|
Normal Condensation or Minor Leak | View Details |
| – |
Hot water runs out quickly from an A.O. Smith tank-type water heater.
|
Reduced Effective Capacity / Stratification Issue | View Details |
| – |
No hot water at all from A.O. Smith gas water heater (no error code on basic models).
|
Complete Ignition or Gas Supply Failure | View Details |
| – |
No hot water from A.O. Smith electric water heater (no digital display).
|
Power Loss or Dual Element Circuit Failure | View Details |
| – |
Water heater leaking from the bottom of the tank.
|
Tank Corrosion / Internal Tank Failure | View Details |
| – |
Water is warm but not hot enough from A.O. Smith gas water heater.
|
Insufficient Burner Operation or Thermostat Misadjustment | View Details |
| – |
Water is warm but not hot enough from an A.O. Smith electric water heater.
|
Single Element Operation or Thermostat Misadjustment | View Details |
| – |
Water leaking from the temperature and pressure (T&P) relief valve on an A.O. Smith water heater.
|
Over-Pressure or Over-Temperature Relief Discharge | View Details |
| – |
Water leaking from the top of an A.O. Smith water heater around the piping.
|
Connection or Fitting Leak | View Details |
No matching codes found
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