Q: Heater on 1996 Ford Ranger

The hose is black and close to the tailpipe. One end connects to a clamp which goes comes down out of the truck. The other end connects to a metal line about halfway under the truck in the middle. What is the name of this pipe?

van wouldnt start, replaced battery. replaced alternator twice. first one was rebuilt, 2nd brand new. it started. but cannot run AC , heater etc. drains battery. then van wont start with out a jump. battery light only comes on when AC is turned on.

I have to put my back window wipers on for my passenger window to go down, the a/c and heater only works while I'm accelerating so basically I have to be going a high speed for it to blow, the radio only works when the car is off so does the front wipers...weird things like that...someone said it was because my automatic doors are off track