my A/C works but only blows through the defrost vents I know this is vacum ontrolled but where do I start also it does not matter whether it is a/c vent or heat it all comes out the defrost vents

 

Try taking the dash off and go from there. Follow the routing and see if the ducts open/close when adjusting the AC head unit. My IROC used to do this, but my dad surprised me and had it fixed one day.

 

that would work but I'd like to figure out the source of the problem before completly removing the dash
if you would ask your dad what he found
thanks

 

There's a vacuum control valve on the back of the A/C control panel that tends to develop leaks over the years....pull the panel out and see if you get vacuum to the different ports when you move the control lever.