Components of a Bus-Air-Conditioner are:
Compressor = the drive shaft is attached to the sub-engine flywheel. It has two reed valves on the cylinder head. One is the intake and the other is the exhaust. When the piston goes down, the intake reed valve opens and the exhaust reed valve closes. When the piston goes up, the intake reed valve closes, and the piston forced the compressed refrigerant to exit the exhaust reed valve thereby producing high compression pressure.
Condenser = is a serpentine coil of copper assembly with aluminum fins for heat dissipation. Heat collected by the refrigerant coming from the evaporator is combined with the heat produced by the compressor, and goes to the condenser so that the heat will be released to the atmosphere with the aide of a condenser fan. When the temperature of the refrigerant drops, so is the pressure; and it turns into liquid refrigerant.
Receiver = is a storage tank for the liquid refrigerant. It is always kept full so that the thermal expansion valve will not run out of liquid refrigerant to feed the evaporator. The temperature and the pressure at this stage is still high, therefore the receiver is equipped with a pressure relief valve, and it will melt and release the over pressure at 96 degrees Centigrade.
Drier/Strainer = has filter and desiccant inside the device. The desiccant will absorb the harmful moisture content in the liquid refrigerant while the filter will catch the small iron particles and dirt in the liquid refrigerant. Both is needed to be assured of a pure liquid refrigerant entering the evaporator and into the compressor.
Sight Glass = is an optical device for us to see inside the sealed glass if the liquid refrigerant is sufficient. If the liquid refrigerant is clear like water, that means to say that our liquid refrigerant is enough; but if we see bubbles in the liquid refrigerant, that means to say that the system need charging of refrigerant.
Expansion Valve = is also called a metering device. It controls the quantity of liquid refrigerant to enter into the evaporator. It has a feeler bulb attached to the outlet of the evaporator. When the calibrated super heat is breached, the volatile gas inside the feeler bulb will push open the inlet valve and let more liquid refrigerant into the evaporator.