Vacuum systems in C280
 

I have a vacuum leak under/behind the passenger dashboard and my vacuum pump in the trunk cycles occasionally (1995 C280). My mechanic tells me that the vacuum pump in the trunk is only for the door locks (which currently work fine) and that the engine vacuum runs the climate control. Is this true that the vacuum pump in the trunk is solely for the door locks. I get hissing under the passenger dashboard which seems to go away when I accelerate. Any ideas?