Armstrong Air Ultra V, 4 yrs old:

Problem:
*Igniter comes on with bright red/blue flame
*Burners then come on
*Fan blower comes on
*Shortly after blower comes on, burners go out, and blower continues to run
*Igniter comes back on
*Burners then come back on
*Then Burners go out again about 5 sec later
*This process keeps repeating itself

Indicator lights show that furnace is working properly. Cleaned sensor, removed filter, put filter back in and it started to work properly again for about an hour. Then furnace repeated problem. Turned off Thermostat and then back on and it started to work again. It has currently stayed on since resetting the Thermostat.

This is the 2nd occurrence of this problem. The first time, we reset both the furnace & thermostat & that fixed the problem until now (2 months later).