I would like to THANK all of you for your generous help in finding a vacuum leak in my 1994 C280.
I found a disconnected white hose near the oil filter area. I believe this is the cause for the air not to blow out through the center vents but at the defrost outlet instead after 2 minutes the car started. This lost of vacuum problem also caused my rear headrests could not be released.
I had this very same problem 3 years ago, and the dealer shop charged lots of money for the parts replacement and labor. I fully believe this caused by the guy who performed the oil change and after replaced the oil filter. A simple reconnection of the vacuum hose with a rubber connector would fix the whole dawn problem.
A problem remains. I couldn't find the place that this white / clear hose was disconnected from ! Could any one help ? A picture show where this hose goes to would be a great help. Many thank in advance.