I just began renting a house and the AC system is automated and it has a little light that blinks FILTER FILTER FILTER...ok so i open up the AC closet, and its this huge brown furnace (with duct tape on the top...thats a concern) but i say hey it works eff it! so i go to replace the air filter and i cant find out where to do it, its built on top or a wooden platform, and under the wooden platform is the two Air return vents (its in a corner and a vent is on either side) i open up the vents and i am looking at VERY DUSTY hole in the wooden platform i cant find the stupid air filter...any ideas??? I am pretty handy, i wouldnt say educated in AC repair or anything but you say open up a return event and do _______ then i can prolly do it just need to know what to do