I have a 1992 Grand Prix and have a question about the heater control. In the heat/vent/defrost positions, the ducting seems to stay the same where warm air blows onto the windshield and down below by your feet only. The fan speeds work fine insofar as adjusting the fan speeds but I'd really like to get warm air through the vent position too. Anyone else had problems like this? Thought I'd come here for help. TIA