My vacuum canister is missing and my ac only runs out of my heater and defrost vents. Is the vacuum canister the problem or do i need to look somewhere else to get this problem corrected? Thanks

 

If the canister is missing and the hose to it is not capped, you have a vacuum leak. Plug the hose to the canister off and your vents will work normaly under light engine load. The canister is there to supply the HVAC system with reserve vacuum when the engine is producing little.

http://shbox.com/1/4th_gen_tech2.html#HVAC_vacuum