Just to expand on Mike's suggestions---if you pull out the glove box, the instrument cluster and the console kick panels (not much work, really) you'll be able to see the floor and defrost vacuum actuators in operation. There's another between the heater matrix and the firewall to control the "rec" (recirculate) vent. Button pushed in closes that vent to fresh air. If that one is working properly you should get air flow while driving from any of the vents set in the open position with that button out. Pushing it in would require the fan to move air through the vents. The face level vents should flow air as long as the individual vents are set in the open position -- does not require "floor" or "defrost" to be open. You should be able to get air through the floor and defrost vents at the same time with both buttons pushed in. For maximum defrost close the floor and face vents.
The control panel is not particularly easy to reach. After removing the console face you need to remove the 4 screws that hold the console frame to the uprights for access to the control panel. They do go bad--usually accompanied by a hissing sound (with engine running) when the offending circuit is actuated. -- Dave