Recirculation Operation
WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in heater through defrost. The operator must activate the blower for Recirculation operation.