I had the exact same problem in my 1988 Tempo several years ago. A/C worked ok, but just wouldn't cool the cabin when aimed at the windshield. Turned out to be a $1.50 piece of plastic that had broken. It was responsible for directing, (perhaps also blending) all the heated/cooled air. Unfortunately, they had to drop the dash to fix it, something like 5.5 hours of labor and it ended up costing me at least a few hundred. Hope you make out better with your situation.
HTH,
Jay
