A.O. Smith 110-310-510 – ERROR CODE 111 [510 (T-D2)], THREE FLASHES/11 (110 [T-KJR2), 310 (T-K4)] IGNITION FAILURE

Heater does not fire after three failed attempts at ignition.
1) Verify that the hi?limit switch is not tripped. Turn the power off to the unit. Push the white button in. The switch will reset when you hear and feel the button click.
Turn the power back on and test the heater. If the unit fires on, the cause of the hi?limit trip must be determined.
Please contact the Technical Service Department for further technical support.
2) Check the gas supply. Verify that sufficient gas is being supplied to the heater and the gas line is clear of debris or any air. Purge the line of air if needed (p. 22).
a. It is possible there is a faulty pressure regulator at the gas meter.
b. For propane units, colder periods of the day result in a cold regulator and may cause this

3) Verify that the gas supply pressure is within specifications when the heater is in standby and when
the heater is running.
4) Check that the clear plastic tube connecting the proportional gas valve to the combustion chamber is attached.
5) The overheat cutoff fuse (OHCF) may have been compromised. For procedures on how to check whether the OHCF is intact, refer to p. 24. If the OHCF has been compromised, contact the Technical Service Department for further assistance.
6) If flame comes on for only 1?2 seconds before going out, clean the flame sensor (p. 25).
7) Check the igniter for a spark. The spark may be viewed through the sight glass located next to the igniter and flame sensor.
a. A strong blue spark will remain steady and in place, while a weak spark will jump around.
b. If no spark or a weak spark is observed, check the igniter wire connections and make sure these are secure. If these are secure, a replacement igniter will be required.
8) Check for blockages in the venting, such as bird nests, animals, or trash.
a. PC Board fault or Gas Solenoid fault. Contact the Technical Service Department.

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