Vacuum line question

[Guanfy]

When I first got my truck I found that I had a rotted vacuum line that went from a plastic pill capsule shaped container on the passenger side of the engine on top of the ac box down to a T of vacuum lines. The line has a very small diameter and I didn't have the right size hose so I capped it at the T and went on my merry way. From what reading I've done it sounds like that little line has something to do with climate control on the truck, but I can't figure out specifically what it does. Anyone known specifically what that line does?

 

[RobbieD]

If I'm not mistaken, the container is a vacuum reservoir and the T fitting contains a check valve. The reservoir stores vacuum supplied from the engine, which is contained by the check valve, and this vacuum supply is used by the HVAC control lever to position the blend door as the lever is moved.

 

[Dirtman]

Little clarification. The blend door is controlled via an electric motor, this what adjusts the temp. The vacuum system controls the vent position. i.e switching from floor vent to defrost ect. With the vacuum line disconnected the vent will only blow on defrost.

 

[Guanfy]

Very good! I suspected from the diagrams I'd looked it the line was related to climate control but not sure specifically what. I'll try to rig up a replacement line this weekend. It left about a half inch nub sticking out of the ac box side I need to rig a line around that then narrow it down to something that will fit on the T check valve.