Looking at the picture, the connection I am holding seems to come from a box under the cover that surrounds the windshield wiper arms,passenger side.

It seems to be broken to the piece also marked which says MPC.

What is this! Id like to fix it when possible!

 

Vacuum lines and check valves.

 

If these are broken what problems might happen? I've got that same issue only both are sitting on my table right now and not even in the truck.

 

All you have to do is take the large parts off and connect the two lines I circled with a vacuum hose from any autoparts store. Have them clip you a piece of each size to fit first.

To answer specifically, I believe its simply for air control so everything functions well.

I havent confirmed this theory,but my a/c position **** (the **** that lets you choose recirculate, blow from upper, blow from lower, or blow from defroster)started working after I put the hose on.

Before, a/c only came out from defroster vents. Now the selection works and a/c can also be selected for upper or lower vents. I believe this is the case because the connection I hold in my hand in the picture seems to go into a box under the outside dash that covers the wiper motor area. I havent found out what the box is for yet,but I would now assume its for a/c ventilation.

 

That seems to be a common issue then, Thanks!

 

Depending on the age of your beast, the plastic line, whats left that you didn't replace, will continue to crack or break.

 

Your 4wd won't work either and maybe cruise control.