[tomj76]

The front air is controlled only by the switch that selects the heating mode, and by the hot/cold adjustment.

The hot/cold adjustment controls a servo motor that allows some air to pass through the heater core after it has gone through the evaporator. The mode selector control another motor that directs it to the desired exit point, (i.e defrost ports, dash board vents, or floor vents). Hot air that's coming from the expected vents implies that there is a problem with the hot/cold adjustment control, either at the knob or at the servo motor.