[yogi_123rd]

Try looking under the hood, on the firewall, near the master cylinder for a vacuum hose going to a vacuum accumulator box. One rubber hose for engine vacuum goes to it and there will be another plastic hose from your heater/ac that connects to it. Your vents in the heater/ac are accuated by vacuum. Check for dryrotted hoses. The default setting on the heater/ac is to send the air out the defroster/heater ports.