Hi, I have a 1986 300E (200,000 miles) and have had many problems on the car. I have fixed some and others, I live with. Latest one is I can't get any heat at my feet. It has never worked since I bought the car 4 years ago. I don't think I have vacuum leak. All other vacuum related systems work. The electrical signal from the pushbutton heater control unit is good and the switchover valve is opening to send vacuum to the servo when heat at feet is selected. There is a metal sintered filter ( restrictor) fitted inside a short rubber hose to which the vacuum line is connected. If I remove this filter, the vacuum gets to the servo and the flaps open and I get heat at the feet vent. With the filter installed, I get no heat. The servo don't move. I think the restrictor is to allow the servo valve to open slowly and maybe plugged. Have anyone ever heard of these restrictors getting plugged up? Could it be that the car is not producing sufficient vacuum or is there a small vacuum leak? Do anyone know what a vacuum gauge should read when connected directly to the manifold? I would really appreciate advise on this.
Thank you in advance