GM Service Manual Online
For 1990-2009 cars only
  1. Start the engine.
  2. Set the A/C temperature control to 32°C (90°F).
  3. Set the passenger temperature control to full warm.
  4. 3.1. If the outside temperature is above 32°C (90°F), disconnect the inside air temperature sensor.
    3.2. Allow 45 seconds for the air temperature actuator (2) to move to the warm position.

    Object Number: 305037  Size: SH
  5. Gently pull the driver temperature door link toward the programmer until the door hits stop.
  6. Push the threaded portion of the link into the slot of the driver temperature door crank.