SFD1248

A friend of mine has an '04 GC. He has a vacum hose that controls the cruise control and the a/c vents. Does anybody know where this hose is located like a hose diagram. He said sometimes he gets in and the a/c blows cold as ice. other times he gets in and it will only blow out of the defrost on the dash. The stealership told him to bring it in for the tune of 75 dollars. The part if it what he thinks it is is only like 15 bucks. Thanks in advance.
A quick answer would be great
Andrew