Hello - Does anyone have instructions how to clean the blower on this model? I recently purchased a house with one of these installed (it is 9 years old). I noticed the previous owner didn't change the filer in some time, so I took care of that, but I fear the blower may not be working as efficient as it should. The unit is on the first floor (the house has 3 floors). And air is coming out fine on the first & second floor, but very weak on the third floor. Can anyone assist me in resolving the issue?