No heat need some help please.
 

The blend door is stuck in the A.C. Position in my truck. It's a 92 f150. 5.0 I would like to know how to get the blend door to a switch from the ac position to the heater position. Last I know the heat worked fine. I had someone try to get the ac in my truck working but the guy never had a chance to finish because I ended up needing the truck back. He said that because of the way the blend door is acting up that I would need to choose heat or ac.This guy has sense moved. He told me that to switch the blend door to heat I needed to do it manually. If someone can show me were its located and how to switch it, it would be greatly appreciated!!