Posessed air conditioning.

The vac feed for the HVAC is probably open. The default with no vacuum (like at WOT when you have no manifold vac) is out the windshield vents.

Trace the line under the hood and you should find the open. It's a very common issue. It's a 30 second fix once you find it.

Good luck.

Mine did the same thing...turns out it was a broken vacuum line that was under the hood. (runs parralel to the firewall, black in color)

Yup, it's most likely the very thin plastic line that runs under the cowl along the firewall from the drivers side corner. There is a vacuum tree there. Once my broke in the middle. The second time it broke a piece off in the tree itself. I ended up getting new tubing at Oreillys and replacing most of it as mine was really brittle.

That does look like a winner.

If you have a piece of rubber vac line that has an ID that fits over the OD of your OEM line, you can splice it. The rubber splice would function like the duct tape did (albeit much better). I've done this and it works decently as a temp fix.

The ducting for the vents is controlled with vacuum. Have you ever gone to WOT for a bit and noticed your vents stop blowing on your face? Once the vac reservoir is depleted, the HVAC controls lose vac (as happened to you with your open vac line). The result is the default setting (air out the windshield vents).

I havent replaced the entire line so I'll let the guys take care of that question.

The following is for a fox but the function is very similar to ours. I think you'll have a better idea of how vacuum plays into things. Thanks to site host S&2B's (I'm not sure who the diagram author is. It might be TMoss):



Good luck.