I arrived for a blue club membership fall tune up. I inspected the system and found that the filter is new. I did replace the fiberglass filter with one of our filters. I then inspected the system and duct work and found all the return duct to be dirty. I found the system to have a 15 deg temperature rise. This system has a lot of returns and can move air quickly and not let the supply air temperature rise quickly but it will move air pretty fast. The supply temperature only got up to 87 deg with a 15 minute run time. I made this aware to the homeowner and that if we can clean and increase both duct systems we can have better air flow and less stress on both systems. The homeowner will let both units run as is for now.