Back during the summer I had my truck(2004 F150 Lariat) at the Ford dealer because my ac would work one day and not the next. They replaced an o ring and charged the system. It continued to work one day and not the next even though I had it back 4 times. Now the heat is doing the same thing. It blows cooler than it used to air regardless of the temp setting. However, tomorrow it might work fine. So, what gives?

 

That's exactly what my truck is doing. I really wish someone would reply......