We recently purchased and installed a Harman XXV pellet stove that my husband is diligent about cleaning. It has only been installed and operational since October 2014 but within the last week the distribution fan has become troublesome. It is making a low whining sound. Not the sound we found posted on youtube associated with auger design. He has noticed that the higher the temperature, the louder the sound becomes. We have referred to the owner's manual but have not had any success with resolution despite all the recommended cleaning. He cleans the window and burn pot out daily as well as vacuuming the entire stove at least once per week. He also cleaned the combustion fan on Sunday after burning the first ton of pellets as per manufacturers instructions in the Harman video we received with our stove. Any suggestions would be greatly appreciated!