Hey thanks for the response. I had no idea that this unit was also incharge of supplying supplemental air to the air climate control system. Today I did notice however, that my passenger side vents were letting cool air come out while only the driver side was pumping out heat. I don't know if this is related to my Vacum pump however. Besides this problem, my air climate control system seems to be working fine. However my door locks don't work at all. I have to manually lock my doors by either pressing down or by getting outside and using the key. I can still roll all four of my windows up using the key, however it makes no effect on my door locks. They have simply stopped working. Also my car will not start up without the vacum, or if I have locked one door and unlocked another by hand, seems like some sort of anti theft type problems. When I connected a c230 pump, the door locks did work, but the car doesn't start. Also the pump was newer, from a 96 c230. After seeing that pump make my doors work fine, I don't know if I have or had a leak in my system. I remember for the last couple years, when my climate control/air was on in the car, I would always hear a buzzing sound near the back seat, at which time I had no idea this part exisited. I asked a mercedes tech, about the humming/buzzing noise, and I was simply told that there was an air intake in the back of the car for climate control. Recently I have been wondering my self why the buzzing stoped, as did my door locks. However I never suspected it to have any links to the Climate control since it was still working fine. Even my recent problem took the mercedes techs 2 hours to figure out, since my windows, all four still roll up and down fine from the driver side door lock with the car's keys. I don't know what happened to my vacum pump centeral door locking system. Is there any help you can provide me with? Thanks.