..............need help..........

Was also thinking it's 2 problems. Resistor for speed issues and blend door problem for airflow. Sounds like door for air intake is closed. Closed normally only when in off or max air settings. I turn mine to off when I get out in winter to keep critters out, especially if your block heater is plugged in as they are drawn to the heater cores warmth.If you do have to get in deep to fix a blend door problem do the heater core at the same time. Job is mostly labour. Google the job for how to do it without discharging the AC lines.

*** Turn heater knob to off before shutting down engine as it is vacuum operated.