91 grand prix

my 91 grand prix only blows air at the feet and windshield. It will respond to the heat setting and the Air coditioner also works. I have heard people talk about 'vacuum' problems. If this is the case, how do i connect the vacuum hose or where is it located? Do i have to take the dash off:comprage1

my 91 grand prix only blows air at the feet and windshield. It will respond to the heat setting and the Air coditioner also works. I have heard people talk about 'vacuum' problems. If this is the case, how do i connect the vacuum hose or where is it located? Do i have to take the dash off:comprage1
I had the same problem and after three weeks called a dealer and was told to look under the battery box where a vacuum line runs to the round vacuum can under the right front fenderwell. Sure enough, the line was frayed and broken. The line repair cured all of my system duct direction poblems. You could also have a problem where the line plugs into the vacuum canister. You can see it from underneath the front bumper assembly.