Air not coming out of the vents in a 1994 chevy astro

SOURCE: WILL NOT SWITCH AIR FLOW STUCK IN DEFORST VENT

when your car is in defrost it has an ac cycling it removes the moisture then sends the air over the heater core depending on how warm you set it you can feel warm or cold but the ac is always cycling...ridding the moisture...you need a good ac tech it will be okay...its just expensive going into the heater core if needed...!

SOURCE: 2002 Astro van ventilation fan problems.

The problem is a 1/8 diameter hose that runs from the front of the engine over the top and connects at the rear of engine on the drivers side. It is a vacuum hose #GM15967970 It cost about $6.22 at your GM dealer. Hope this helps Bill. My E-Mail is [email protected]

SOURCE: 2000 chevy astro van front a/c switch is out - don't push airout

As for the air only blowing out of the defrost, your problem is not the switch it will be a small vacuum line that runs from the top of the engine directly behind the a/c compressor to vacuum tank located on the passenger side of the engine compartment just to the right and forward of the engine block. It is a small black tube. Once you find the break, a splice connector costs about $.20 at the parts store.

As for the fan not blowing on all speeds. Sounds like a resistor located in the blower motor housing under the hood passenger side. I just replaced mine. Costs about $45 and fixed the problem. Although these do go out with age, sometimes they indicate excessive load from the blower motor itself. If it happens again, look at that.

SOURCE: AIR FLOW STUCK IN DEFORST VENT WILL NOT SWITCH TO FLOOR OR AC VEN

I found a broken vacuum hose on top of the intake which runs the controls

SOURCE: All Air Conditioning blows our the defrost vents

Some thing you could look at would be this. The control is usually fed by a vacuum line or small hose thats is connected to your intake manifold.
With a cold engine,look for a skinny vacuum hose that runs from the intake toward the fire wall . It should be going inside the cab and connecting to the A/C vent control.Some times the hose becomes disconnected or splits or cracks due to heat under the hood.
Thats usually the trouble.
I hope this helps you.