Automatic Temperature Control: Description
During diagnosis it is important to remember that 1973 air conditioning is functionally different than earlier systems as follows. Low blower continues to operate in heater mode when in the "Off" position at all times, except when both engine and car's interior are cold. The "Bi-Lever" setting provides both upper and lower level air simultaneously, otherwise it operates the same as "Auto" position. The "Def" lever setting provides fixed high blower air from defroster outlets and a bleed out heater outlet, otherwise it operates similar to "Hi". Testing procedures and adjustments are performed in the same manner and sequence as on previous models. The Fleetwood 75 Series rear system remains unchanged. The Eldorado A/C system is identical with all other series and does not require different or special tests or adjustments.
A noteworthy compressor protection system has been added to all General Motors A/C systems. Termed by Cadillac "Low Refrigerant Detection System", the system will be described and explained in a later paragraph in this article, and illustrated by a circuit diagram.
All Cadillac vehicles, whether equipped with A/C or not, incorporate a positive constant ventilation system. Whenever the ignition switch is on and the engine running, the blower motor is running at LO, and with either the A/C system (if equipped) or Heater System OFF, fresh outside air is drawn into the car and discharged either through grilles near the cowl side trim panels or through a grille in the instrument panel. Air in the vehicle is exhausted through grilles in each door lock pillar, thus providing a continuous supply of fresh air in the passenger compartment.