Plastic Vacuum Tank

[budro]

What is the purpose of the plastic vacuum tank or reservoir on top of the Plastic housing covering the Evaporator or AC Box? It has a leak and lets the max air valve not hold down to keep circulating air inside the cab. I just plugged the line going to it and it seems to be working fine.

 

[AllanD]

It's to keep a supply of vacuum for the blend door inside the cabin in
position when the engine is NOT making vacuum...

If your door doesn't work it could be the actuator inside the cab, any of the lines or the check valve that prevents air from flowing the other way.

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