Hello all. I have had the above stove for a few years now. Not a bit of problems in all that time, with burn pot maintenance, ash pan removal and vacuuming the unit diligently. This season, prior to start up, I vacuumed the stove and fired it up, all the time running on manual (a thermostat option is installed on this unit, but has never been used). It ran for about a half hour with a nice fire in the box- pellets burning completely and a nice heat, happy and warm once again. Then the nice fire went to a lazy high flame! Door gasket is tight, we adjusted the air flow - no help. We removed the exhaust blower and cleaned the fins, reinstalled it and fired it up again - after getting up to operating temp again we get the lazy flame. We disconnected the hose from the brass fitting on the exhaust unit (it was clear) blew thru the tubing (no restrictions) to the flow switch. Jumped the switch, in case of a ruptured diaphragm - no change in the lazy flame height. Any help or suggestion as to the problem would be greatly appreciated.