1996 E320 A/C Vacuum System and Air Recirculation Changeover Valve Problem..

[waleedshams]

hello
i have a 1996 E320
the problem is with the air recirculation, when i press the button it does nothing and the air keeps coming from outside the car.
i removed the glove box and the blower fan and i found the
changeover valve" (part # A2028000178)
i test the electricity coming to the valve, the electricity is coming constantly when the button is pressed or not, and i checked the valve in my home using a 12v adapter, i can hear that it's working.
the green vacuum hose which is coming from under the hood doesn't have any air inside it. i checked under the hood and i found a distribution box for the air hoses " with different hose colors ".

so please explain to me where is the problem exactly, is it in the vacuum system or in the switch.
should the green hose have air pressure or not?

sorry for my poor english..

thanks