Red vacuum line along fire wall

[hsmith]

I just finished replacing the heater blower motor in my 1984 190d. While doing that I noticed a red vacuum line that runs through the firewall on the drivers side over to passenger side where it is attached to a round something on a heater hose. My car blows only hot air throught the vents, and the flaps do not work. From what I have been able to find out so far is that I might have a vacuum leak. It's not the climate control unit because I just replaced that too. I took the red line off the round thing and checked the round thing for vacuum - it holds vacuum. I checked the red line for vacuum and the vacuum slowly decreases. When I cranked her up my Mity Vac did not show any vacuum on the red line. Does this mean that I probably do have a vacuum leak somewhere in the climate control vacuum system? Thanks

Hugh Sr.

1984 190d (W201) 132,432