HVAC vents not changing

[Jakegday]

hey guys. 2001 grand prix here. I went to use my A/C last night when i noticed the MAX A/c wasnt working. It would blow cold air, but it would not go into recirculate mode. Then after that i noticed air just came out of the front vents and floor only, no matter what position the switch was in (floor, vent, defrost) The switch still makes the a/c compressor kick on when its switched to max a/c or defrost, but the vent position does not change. I checked all vacuum lines under the hood and everything looks fine, although i couldnt find one specifically that goes right to the HVAC unit. I paid special attention to the areas around the spark plugs and wires i recently changed, but couldnt find anything suspicious.

Im basically wondering, for anyone who has experience with these cars, where the vacuum line for the HVAC is?
any other suggestions on this issue will of course be welcome..

 

[The_Jeff]

On my silhouette it was 1/8" semi hard (yet flexible) black nylon/ plastic line that met little 90 degree rubber elbows.

 

[ron350]

It sounds like you knocked the vacuum line off where it plugs into the intake manifold.

First find your vacuum ball and trace the vacuum line to where it goes into the fire wall.
On earlier W- bodys the vacuum ball is in the driver’s side fender in front of the tire.

There should be a check valve vacuum (T) in line below the throttle body up against the fender.
Those check valves are known to go bad or break easy.

 

[Jakegday]

I figured it out. apparently the vacuum line goes from the engine, to near the battery, where it joins a wiring harness which goes through the firewall. because it runs near the battery, it is in the perfect spot for corrosion from the battery to fall on it, and cause it to corrode/melt