Ok so it started out as an AC problem at the end of the summer. It would just blow air-not hot or cold- most of the time, and sometimes it would get cold..then go back to just air. Now it's doing the same thing with the heater. Sometimes its hot sometimes its just air. Any help? Do I need to add antifreeze maybe? If so how much? Thanks to anybody with advice! really don't wanna have to take it in!