Electrical Systems - Chassis --- Section 9
The Executive 2005
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R-134a Refrigerant:
R134a is classified non-explosive, non-flammable and non-corrosive.
R134a is ozone friendly; however, it is not technician friendly. Proper care in handling must be
observed. Under normal atmospheric pressures and temperatures R134a will evaporate so quickly it will
freeze anything it comes in contact with. The open container boiling point for R134a is minus 21.7º F.
This low boiling point makes for an ideal refrigerant. The tremendous amount of heat transfer which
occurs when a liquid boils, or vapors condense, forms the basic principle of all A/C systems. The
amount of heat required to raise or lower the temperature of one pound of water by 1º F equals one
British Thermal Unit (BTU). The BTU is the standard measurement of an air conditioner system.
Safety and Handling of 134a and Pag Oil:
• Wear eye and hand protection.
• Pag Oil irritates the skin. Flush with water immediately if in contact with any body part.
• Ensure all service work on the A/C system is performed in a well ventilated work area.
• Keep open flame away from service area. The discharge of a refrigerant near an open flame
can produce a poisonous gas.
NOTE:
O-rings required for the 134a system are Hydrogenated Nitrile Butadiene Rubber
(HNBR), and are green in color.
Air Conditioner Refrigeration Components:
Compressor - The compressor is belt driven from the engine through the compressor and elec-
tronic clutch pulley. The compressor will pump freon from a low pressure gas into a high pressure,
high temperature gas. This is the start of the refrigeration process.
Condenser - The condenser in front of the radiator is made of coils and fins which provide rapid
transfer of heat from the refrigerant as external air passes over the coils. The high pressure gas is
changed to a high pressure liquid.
Condenser Fan - A steady flow of cooling air is maintained across the
condenser during system operations. The fan is part of the hydraulic system.
Receiver-Drier - Freon leaves the condenser, enters the dehydrator and is stored until needed. The
drier filters out moisture in the system. It only takes one drop of moisture to cause a malfunction in
the cooling unit.
Expansion Valve - The expansion valve suppresses the refrigerant into the evaporator according to
the cooling requirements. The pressure is reduced in the restrictive effort of the expansion valve. A
part of the valve is the capillary tube assembly. The capillary tube is the sensing bulb at the outlet
of the evaporator.
Evaporator - A tube core and fins are used in the evaporator similar to the condenser. Air is blown
through the fins to allow the evaporator to cool and reduce the pressure.
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