Most models are equipped with a bypass heater water valve. When the air conditioning is turned ON, or heater is turned OFF, the vacuum operated heater valve closes off the hot water flow to the heater core.Low Pressure Switch
The low pressure switch is designed to shut off the compressor should the pressure in the system be too low to maintain proper lubrication.
The compressor used with this system is a high speed unit and requires lubrication at all times. Do not override or bypass the low pressure switch when the system is not capable of maintaining sufficient pressure to circulate the lubricant.Dual and High Pressure Switch
The dual and high pressure switches are designed to protect the system and compressor from excessively high and low pressures. Should the pressure in the system be too low to maintain proper lubrication or be excessively high, the compressor is shut off.Receiver/Drier
The receiver/drier is a reservoir used to store refrigerant required by the system. The receiver/drier should provide an adequate and steady flow of liquid refrigerant to the expansion valve. The receiver/drier contains a dessicant to remove moisture from the system and the assembly should be replaced anytime the system has been opened to the atmosphere, due to the immediate entrance of moisture and foreign material.Condenser
The condenser is mounted in front of the radiator core to allow air to flow over the cooling fins and remove the heat from the refrigerant, allowing the refrigerant to condense (liquefy).Evaporator
The evaporator is encased in a housing and is mounted under the dash panel. The evaporator is used as an air cooler and dehumidifier. The heat in the air passing over the evaporator fins, transfers or gives up its heat to the boiling refrigerant within the evaporator coil. As the air is cooled, the moisture in the air condenses on the evaporator core and is drained off as water.Expansion Valve
The thermostatic expansion valve is located at the inlet of the evaporator and meters the refrigerant into the evaporator coil, so as to maintain the proper flow for the various evaporator heat load requirements encountered during the vehicle operation. The metering action of the expansion valve is controlled by the temperature sensing bulb, mounted on the outlet (suction) side of the evaporator.Compressor
The compressor is a typical belt driven rotary unit. The type may vary on different vehicles, but the basic operation is the same for all the compressors. The compressor is controlled and connected to the engine through a electromagnetic clutch and drive belt.Service Valves
There are 2 service access gauge port valves on the system. The high pressure discharge port is located in the discharge line near the condenser. This port requires the use of a high pressure gauge adapter. The other service port (low pressure side) is located on the low pressure side of the system and is used to measure evaporator pressure.