The sun load sensor is a light-sensitive photo-diode that is used to monitor the heat load of the sun on the vehicle. The sensor is located in the defroster grille where the sunlight reaches the sensor. As the sunlight intensity increases, the conductivity of the sensor increases.

The heater and A/C control module monitors the sun load sensor and uses this information in order to vary the in-vehicle temperature in order to compensate for the increased solar heat.