There seems to be something wrong with the gas flow/valve, burner, or sensor.
I can see the electronic ignition element turning white hot, then hear the gas valve click on, then see the blue gas flames light for a second or two before sputtering out. This cycle repeats itself several times until, the system "gives up" (or I guess locks out) at which point the blower just continues to blow cold air forever and no further ignition attempts are made. The blower continues to blow even if I shut off the thermostat
Interestingly, if I cycle off the power (even just for a second or two), the furnace will start up normally and ignite the burners properly. The burner will continue to fire for a *couple of minutes* before blowing out at which point it goes into the (failed) cycle of trying to relight a couple of times before finally giving up and again leaving me in the stuck state with the blower blowing cold air.
Sometimes in the cycle of trying to re-light it will burn for a few seconds before sputtering out. Also, sometimes, I hear the valve clicking on-and-off a couple of times in rapid succession.
Now the other two gas furnaces are working properly, so I don't think it is a supply problem. Also, I don't think it is a ventillation problem because it seems to burn fine for a few minutes with a nice blue flame before suddenly sputtering out.
When I opened up the bottem panel (overriding the disable switch), I noticed that after it locked up in the continuous blower position, the diagnostic LED exhibited a pattern of 8 short (red) flashes -- I believe this simply indicates that the flame is lost 5 times within a heating cycle which according to the online manual indicates either: Low gas pressure (unlikely since other two gas furnaces in the house work fine, right?) Faulty gas valve Dirty or faulty flame sensor Faulty hot surface igniter (unlikely because the flame does ignite, right?) Burner problem
Any idea what might be wrong and how to fix?
Even if this is not a DIY fix, I would like to have some idea of what the potential problems could be so that I can intelligently engage the service person and make sure that I am not being taken :)