Refrigeration System
ACCUMULATORThe accumulator functions as a liquid/vapor separator that receives refrigerant vapor, some liquid refrigerant and refrigerant oil from the evaporator. It only allows refrigerant vapor and oil to continue on to the compressor.
At the bottom of the accumulator is desiccant that acts as a drying agent for moisture that may have entered the system. An oil bleed hole is also located near the bottom of the accumulator outlet pipe to provide an oil return path to the compressor. The accumulator is replaced only as a replacement assembly.
COMPRESSOR
Compressors are belt driven from the engine crankshaft through the compressor clutch pulley. The compressor pulley rotates freely, without turning the compressor shaft, until an electromagnetic clutch coil is energized. When voltage is applied to energize the clutch coil, a clutch plate and hub assembly is drawn rearward toward the pulley. The magnetic force locks the clutch plate and pulley together as one unit to drive the compressor shaft.
All replacement compressors from service parts will have oil in the crankcase. The oil must be drained and retained. Replace the oil in the same amount as previously recorded from the old compressor.
CONDENSER
The headered tube and center type condenser is made of cross tubes, that carry the refrigerant, and cooling fins, which provide rapid transfer of heat. The air passing through the condenser cools the high-pressure refrigerant vapor causing it to condense into a liquid.
EXPANSION (ORIFICE) TUBE
The plastic expansion tube contains a fixed diameter tube with a mesh filter screen at either end. It is located in the evaporator inlet pipe. It creates a restriction to the high-pressure liquid refrigerant in the liquid line, metering the flow of refrigerant to the evaporator as a low-pressure liquid. When the engine is turned OFF with the air conditioning operating, the refrigerant in the system will flow from the high-pressure side of the expansion tube (orifice) to the low-pressure side until the pressure is equalized. This may be detected as a faint sound of liquid flowing (hissing) for 30 to 60 seconds. This is a normal condition.
When system diagnostics indicate a restricted expansion tube, it may not be necessary to replace it. Metal chips, flakes, or slivers found on the screen may be removed with compressed air. The expansion tube may be reused if:
- The plastic frame is not broken.
- The expansion tube is not damaged or plugged.
- The screen material is not torn.
- The screen is not plugged with fine gritty material.
EVAPORATOR
The evaporator cools and dehumidifies the air before it enters the vehicle. High pressure liquid refrigerant fl6ws through the orifice tube into the low-pressure area of the evaporator. The heat in the air passing through the evaporator core is lost to the cooler surface of the core, thereby cooling the air. As the process of heat loss from the air to the evaporator core surface is taking place, any moisture (humidity) in the air condenses on the outside surface of the evaporator core and is drained off as water.
HEATER CORE
In any air conditioning mode, the heater core heats the cool dehumidified air to achieve the desired air temperature. The position of the control assembly temperature knob determines how much heat is added to the incoming air.
HIGH PRESSURE RELIEF VALVE
The compressor is equipped with a pressure relief valve as a safety factor. Under certain conditions, the refrigerant on the discharge side may exceed the designed operating pressure. Exceeding this pressure limit may cause refrigerant loss. To prevent refrigerant loss or system damage, the valve opens automatically at approximately 3036 kPa (440 psi). When the valve opens, current to the compressor clutch is interrupted. Any condition that causes the valve to open should be corrected.