AO SMITH TANKLESS WATER HEATER Error Codes
AO SMITH tankless Water heater Error Code List
AO Smith tankless water heater error codes typically point to specific issues like ignition failures (e.g., 111, 121, 991), sensor problems (e.g., 03, 05, EEE), or other component malfunctions.
To troubleshoot, first try resetting the unit by turning the power off and on, then check for obvious issues such as gas supply or vent blockages. For more complex problems, you may need to clean components or consult SPS Plumbing for more help.
To troubleshoot, first try resetting the unit by turning the power off and on, then check for obvious issues such as gas supply or vent blockages. For more complex problems, you may need to clean components or consult SPS Plumbing for more help.
NOTE:
If you have any concerns about your own or someone else's safety, please stop troubleshooting and call SPS Plumbing immediately.
111, 121, 991
Ignition failure, flame failure, or vent blockageCheck and open the gas supply valve. Clean the igniter and flame sensor. Inspect and clear any debris from the exhaust vents.
03, EEE
Heating element or sensor issue
Tum off power and check heating elements for continuity with a multimeter. Inspect sensor wiring for loose connections or damage.
05
Temperature sensor/thermistor fault
Tum off power and inspect sensor wiring. If wiring is intact, test the thermistor's resistance.
72
False flame detectionClean the flame rod. Check for leaks from the heat exchanger and ensure the condensate drain is installed correctly for indoor models.
611, 621
Fan motor or exhaust fan motor fault
Check for loose wires, dust buildup, or corrosion in the fan motor. Check for burn marks on the control board.
33, 34, 52, 61
Various sensor or fan motor issues
These codes can indicate problems with the outgoing temperature sensor, combustion air temperature sensor, modulating gas solenoid valve, or combustion fan. Check wiring, sensor resistance, and fan operation.
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