My air handler is in the attic, and a while ago I had tried to find where the filter goes and was unsuccessful. I'm ready to try again because I'm really sure it needs replaced by now. Despite my best efforts, I can't figure out what size I need. Yeah, I know, go up there and find out. It is just sooooo hot outside! I'd like to only climb up there once, also because the attic ladder is creepy and rickety. I have an ARUF364216, according to the receipt, and online the specs say the filter part number is FIL 48-61, but so far I've found three different dimensions for it: 19x24, 19x22, and 22x24. Anyone know which it should be for sure?