2002 Taurus/Sable Climate Control System Workshop Manual

The amount of moisture (water vapor content) that the air can hold is directly related to the air temperature. The more heat there is in the air, the more moisture the air can hold. The lower the moisture content in the air, the more comfortable you feel. Removing moisture from the air lowers its relative humidity and improves personal comfort. Effects of Pressure on Boiling or Condensation As the pressure is increased on a liquid, the temperature at which the liquid boils (converts to gas) also increases. Conversely, when the pressure on a liquid is reduced, its boiling point is also reduced. When in the gas state, an increase in pressure causes an increase in temperature, while a decrease in pressure will decrease the temperature of the gas.
Compressor Anti-Slugging Strategy (CASS) Liquid refrigerant may accumulate in the A/C compressor under certain conditions. To alleviate damage to the A/C compressor, the compressor anti-slugging strategy (CASS) is utilized. CASS is initiated only under specific conditions: the ignition is off for more than 8 hours the ambient temperature is above -4° (25°C F) battery voltage is above 8.5 volts during engine cranking When these conditions are present, the powertrain control module (PCM) will activate the A/C control relay prior to the engine cranking. The A/C control relay engages the A/C compressor for approximately 4-15 revolutions of the A/C compressor or a maximum of 2 seconds (depending upon vehicle application), allowing the liquid refrigerant to be pushed from
the A/C compressor. CASS is initiated by the PCM regardless of the function selector switch position. The Refrigerant Cycle During stabilized conditions (air conditioning system shutdown), the refrigerant is in a vaporized state and pressures are equal throughout the system. When the A/C compressor (19703) is in operation it increases pressure on the refrigerant vapor raising its temperature. The high-pressure and high-temperature vapor is then released into the top of the condenser core (19712).
The condenser core, being close to ambient temperature, causes the refrigerant vapor to condense into a liquid when heat is removed from the refrigerant by ambient air passing over the fins and tubing. The now liquid refrigerant, still at high pressure, exits from the bottom of the condenser core and enters the inlet side of the evaporator core orifice (19D990). The evaporator core orifice is the restriction in the refrigerant system that creates the high-pressure buildup upstream of the condenser core and separates the high and low pressure sides of the A/C system. As the liquid refrigerant leaves this restriction, its pressure and boiling point are reduced.

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