I have a 75 el Camino that doesn't blow air, (or just very little air) out of the vents or defrost vent. The floor vent for heat does work, but not very good. And sometimes it feels like the heat is always on. This is an ac car, and the ac does work minus the air coming through the vents. Also, the highest speed for the blower motor doesn't work. Have any of you guys run into this problem before? What did you have to fix?