Here is the "weirdest" call I've been on [weird stupid]. Central a.c. not cooling very well. It was a tenant that finally got LL to pay for a service call. I found a slight bit of ice on evaporator coil. Filter, blower, and coil were all clean. Outdoor ambient temperature was in the 80s. I was getting a decent enough indoor temperature drop [17 or so]. This was nearly 20 years ago...I didn't know cfm checkout, yet. All registers were open and unobstructed. It was belt-drive blower running at full amps, belt and bearings okay....hmmmmm. I checked refrigerant charge to find it slightly low [outdoor dry bulb of 83, indoor wet bulb 70.....I was getting 29 superheat but wanted a 23]. One shot of R22 brought my superheat to what I wanted. I was baffled. I went back to furnace for one last look.....I had already checked blower rotation and found it going in the proper direction.....and besides, it had not been serviced in years and it takes a lot more work reversing rotation on a belt-drive than a reversible direct drive. Wait.....the blower was going in the direction shown on the housing [and it was a direction arrow factory-scribed into the metal].....but it was in the wrong direction! I wish I would have remembered the furnace make.....even though I'm new to this site and don't even know if it is proper to list make.....but it was not a big name. It seems to me that it was one of those makes I had rarely or maybe never seen before.....but it was weird! I got it in right direction.....I got my Sanford marker and corrected rotation scribing.....re-adjusted R22 charge.......and tenant could not believe airflow. She had lived there 5 years and it had never been anything like that.