Dash vent air source

[71SilverStar]

I have a 71 T/A, w/o A/C.  I'm in the process of restoring it and discovered something odd to me.  The dash air louvered vents do not seem to be connected to the powered blower system.  They appear to only get fresh air from inletss in the cowl area.
This means no air enters those vents unless the car is in motion.
When the blower is running, air comes in from either the defrost or the lower center air supply (by your feet).  (Depends on where you select it)
Was this really by design?

[5th T/A]

Short answer is yes, this is how they are.

The same time GM did away with vent windows they added ventilation using the outboard dash vents. This was only on non-AC cars. There were two knobs at the top of the kick panels. The upper knob opened and close the dash vents. The lower knob opened and closed the kick panel vents. These vents were not connected to the heater/defroster system. The air for these vents came through the cowl, the faster you drove, more air would come out of the vents. Just like when you had a car with vent windows, they don’t do anything unless you are moving.

[b_hill_86]

I have an A/C car. I never knew that.

[roadking77]

Good Info. I knew about the "Astro Ventilation", and I have seen the pull out knobs on the kick panel, had no idea one was for the dash the other was for the kick!

[71SilverStar]

Well, that explains it then!  Thanks for that!
Guess I won't go trying to fix something that ain't broke...