Volvo Repair: 1991 740 ac, rubber elbows, rubber elbow

Question
I my ac is great until i accelerate then it quits coing out the vents i was told to check the valve on the exhaust manifold...where is this valve? easy to change???

Answer
Probably a vacuum leak, but on the intake manifold or at the firewall. I believe there are a couple of rubber elbows at the passenger side firewall (under the hood)but in general you are looking at a loss of vacuum probably under the hood and probably from a rubber elbow, exact location tba. You wont find anything on the exhaust manifold