Component and System Operation

ACCUMULATOR
The 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 the 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 serviced only as a replacement assembly.

COMPRESSOR
The Harrison HR100T and HR110-MD (CCOT) compressors are driven by a belt 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. Then replace the oil in the same amount as previously recorded from the old compressor.

CONDENSER
The headered tube and center type condenser is made up of cross tubes, which 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 is a plastic assembly containing a fixed diameter tube with a mesh filter screen at either end. It is located in the evaporator inlet pipe. The fixed diameter tube 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 and 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 and 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 is a device which cools and dehumidifies the air before it enters the vehicle. High pressure liquid refrigerant flows 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 can be used to heat the cool dehumidified air to achieve the desired air temperature. The position of the control assembly temperature selector will determine how much heat will be added to the incoming air.

HIGH PRESSURE RELIEF VALVE
The compressor is equipped with a pressure relief valve which is placed in the system as a safety factor. Under certain conditions, the refrigerant on the discharge side may exceed the designed operating pressure. To prevent system damage, the valve is designed to open automatically at approximately 3036 kPa (440 psi). Any condition that causes the valve to open should be corrected, and the refrigerant should be replaced as necessary.