I have a 2006 trane furnace and it keeps blowing cold air! The temp on the screen alwasys goes back to 69 degrees, so I turn it up because it is so cold in my house. It stays at the temp for a couple hours then goes back down. I had just went out for a couple hours and when got back home the temp in my house was 51 degrees! Even though the temp in the bottom corner says it was going to stay at was 69! I turned it back up and it hasn't went past 56 now! I have had nothing but problems with it since I had it up in! I can't figure out how to get it to stay set past 69 or anything either! I have a 4 month old baby so I can't have it this cold in my house! Any ideas to what it could be would be wonderful

Look for a status light on the front/blower panel. This is the shortcut to the problem. There should be a label on one of the panels with codes & instructions.