Contents Wiring diagrams Section: Automatic HVAC System All sections

HVAC System - Automatic: Overhaul Saturn Aura I

Sun Load Sensor Assembly

The sunload sensor is a 2-wire photo diode. The vehicle uses a single sunload sensor. The sensor is integrated into the sunload sensor assembly along with the ambient light sensor. Body ground and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and very bright. The sensor signal varies between 0 and 5 volts. The body control module (BCM) converts the signal to a range between 0 and 255 counts. The sunload sensor provides the HVAC control module with a measurement of the amount of light shining on the vehicle. Bright or high intensity light causes the vehicles interior temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

Mode Valve Assembly

The film valve system has several operating characteristics

  1. The cycle time for a mode change will vary based on the starting point of the film valve relative to the requested mode position.
  2. The maximum time to achieve a mode change occur when the film valve travels between vent and defrost.
  3. Mode change times may very slightly based on variations in system airflow, temperature and voltage.
  4. The amount of air rush noise heard when a mode change is requested that causes the film valve to move through 3 or more primary modes is dependent on blower speed.
  5. Recalibration will typically occur when the engine is OFF. The actuator noise heard during recalibration may be more noticeable than during normal operation.