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Home >> Cadillac >> 1969 >> Calais Not Available, Automatic Trans >> Repair and Diagnosis (Single Page) >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Automatic Temperature Control - Rear Unit >> Control Components >> Vacuum Circuits

Vacuum Circuits

There are two basic vacuum circuits used in the rear unit. The first circuit is modulated by the transducer and operates the power servo. The second circuit is engine vacuum and flows through the check valve, the OFF-ON switch and to the servo vacuum valve. (See Figure).