GM Service Manual Online
For 1990-2009 cars only
  1. Start the vehicle.
  2. Set the temperature to 32°C (90°F) at the heater and A/C control.
  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 temperature sensor.
    3.2. Allow 45 seconds for the air mix valve actuator (2) to move to the warm position.

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