My heater has an issue that has progressed and it is now non-functional. I've had it since 2010, it was running as expected up until this season. What I noticed was when it reached the desired (set) temperature it would click on and off rapidly, almost as if it didn't know if it should be running or not. This only happened as it reached the stopping point. It would start and run normally until that point.
Now it will fire up for a few seconds, I can hear the sparking continue even after the gas is burning; then it immediately shuts off and gives 3 red flashes which indicate an ignition lockout.
I've tried running the pump on high and it does the same thing, so this isn't a flow issue.
Does this sound like an issue that could be resolved by replacing the temp sensor or ignition controller?