I have a 97 F150 lariat with the 4.6 V8 and I have no heat, I checked the coolant levels and it wasn't drastically low, maybe 3/4in below the full line any ideas before I start tearing it apart replacing parts?

 

If you dont smell coolant and cant see any obvious leaks then it might just be your blend door malfunctioning. Check fuses and when its real quiet with the key in the "on" postion you can hear the door adjusting when you mess with the temp.

 

Could be a plugged heater core. may need to be back flushed.

 

when I turn it on to use the AC it makes an audible noise almost like a door opening.