Started happening a couple of weeks ago randomly. Now more frequently. I went to troubleshooting. Cleaned all inside including the vacuum switch on inside of stove. Cleaned exhaust motor. Cleaned combustion fan. Took out many dust bunnys there. Right after all this, turned on. Worked for an hour and boom. Off e-3. My pellets are different from a week ago but was happening with the other pellets before too. My settings are 3-2-1. Also noticed that it said should be run in d mode. How can I tell if im in d or c mode? Any other suggestions. The flames are running intermittant high then normal.