91 Cavalier heating probs

Hi all,
My 1991 Cavalier only blows air through the dash vents. This is a problem since I live near Chicago and really need the windshield defroster to help clear the windshield.
I thought perhaps a cable broke, but I doubt it now as the tension on the lever seems to be the same as before when switching the output from heater(feet) to vent(face) to defroster(upper dash to heat the windshield). No matter which setting I select, it only blows the hot air through the dash vents which point at the driver's face.
Is this a vacuum issue somewhere? If so, where?
What should I check to see if I can solve this problem?
1991 Cav 2.2L 4cyl Auto Trans Has A/C
Many, many thanks!!
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@yahoo.com says...

By law if vacuum was lost it should of defaulted to the windshield I would think... Had a radio put in lately?
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Nope. Still has the stock AM/FM cassette.
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Check the vac hoses at the firewall and where they connect to the engine some GM vehicles route a vac hose close/around the battery and I have seen a leaky battery eat right thru the vac line
Hope this helps
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OK, will do. Any tips on the best way to investigate this sort of thing? Sorry if I'm too clueless!
Thanks!
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As the other poster asked ( about a new radio being installed ) has anybody recently worked on the car, especially under the dashboard ?
Have the engine running, then.......
Poke your coconut under the dash & listen for a SSSSSSSssssssss sound. You may have to remove some of the black lower dash trim panels or posiblly the glove box insert. Any car I had that had a blown diaphram, you'd hear SSSSSSssssssss.
Try sliding the control knob back and forth to vent, heat and defrost and listen for a vacuum leak or any other noises.
Sounds like one of those vacuum diaphram / controls is not operating correctly so the blend door that directs the heat to the floor and defroster isn't moving.
Could also be a loose or disconnected hose.
========Harryface ======== 1991 Pontiac Bonneville LE, 3800 V6 _~_~_~_~275,068 miles_~_~_ ~_~_
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On Sat, 10 Jan 2004 01:43:23 -0600 (CST), snipped-for-privacy@webtv.net (Harry Face) wrote:

Nope. No recent work done at all.

OK, I'll do as you advise. Many thanks!!
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I have a 90 Cav, and it had a similar problem. As well as My Buick, and My Oldmobile. The blower system relies on the "vacuum" system of the engine. There is a single hose that connects to the "vacuum" hoses under the hood. Location somewhere behind the intake manifold.
Anthony...

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