Document jyOXnaKYEXEqBxMYqVaDrB1b2

NAPA AUTOMOTIVE CAREER TRAINING Passenger Comfort - Air Conditioning - Continued Evaporator ary control valves help sense and further regulate evaporator pressure to prevent freeze-up during operation. From the evaporator, the low-pressure gas is sucked to the compressor where the cycle is repeated. Hose and Fittings Figure 23 The evaporator (Figure 23), like the condenser and radiator, is of finned tube construction. On factory installed air conditioners, the evaporator will be built into the firewall. On field installed units, it is attached to the underside of the dashboard. Figure 26 The expansion valve sprays liquid refrigerant into the lower pressure inside the evaporator. Once inside the evaporator coils, it changes from a liquid to a gas. This change allows the Freon to absorb heat, pro ducing cold. A fan behind the evaporator blows air through the fin tubes, producing the cold air felt in side the passenger compartment of the car. All components of the system are connected with hose or tubing to form the complete sealed system. A special refrigerant hose is required for Freon trans mission. The unique feature of rubber Freon hose is in the compound used for the inner lining. This compound is especially made for the Freon and any other rubber hose will break down. (Figure 26). Refrigerant hose, as supplied by the car manufact urers on factory equipment, is always of double-braid rubber or braided nylon. Braided nylon (Figure 27) will be found only in some Ford and Chrysler liquid or suction lines. Nylon liquid hose assemblies are Various manufacturers use different methods of available for certain Ford applications, but most regulating evaporator pressure, thereby controlling nylon assemblies should be replaced with rubber. the rate at which Freon will boil or evaporate inside the unit. Typical is the General Motors' suction throt The hang-on or after-market air conditioner manu tling valve (Figure 24) (STL Valve or POA Valve) and facturers use single braid hose exclusively. Single Chrysler Corporation's EPR Valve (Figure 25) braid is probably selected because it is less expensive. (Evaporator Pressure Regulator) and ETR Valve It is strongly recommended that all replacement be of (Evaporator Temperature Regulator). These second- the double braid hose for maximum protection. 32