Understanding Your A/C System

Posted by Cheolwon Byeon on


The compressor is the main component of the system. It pressurizes the refrigerant so it can flow through the system. Since it is one of the few moving parts in the A/C system, it needs a constant flow of refrigerant and clean lubricant to prevent it from failing. A loss of refrigerant decreases lubricant flow back to the compressor and is likely to cause it to overheat and fail. When a compressor fails, it will cause small metal shavings and debris to be pumped into the system.



The pressurized refrigerant, as vapor flows from the compressor to the condenser located in front of the radiator. The condenser must have proper air flow across it at all times to release the heat that has been absorbed from the passenger compartment. This is especially true when a vehicle is sitting at idle. When a compressor fails, the resulting debris can be trapped in the very small passages of the condenser. At any time this happens it is necessary to flush or replace the condenser to remove any debris that will continue to damage the system.

If the condenser cannot release heat efficiently, additional heat cannot be absorbed from the passenger compartment. 


Orifice Tube (if equipped)

The orifice tube drops the pressure of the liquid refrigerant coming from the condenser to make it cold. It is also designed to trap small amounts of of contaminants found in every system, keeping them out of the evaporator. When the compressor fails, debris that make it through the condenser will be trapped in the screen of the orifice tube. As the orifice tube screen becomes clogged, the pressure in the condenser can get dangerously high and strain the compressor. Refrigerant and lubricant that would normally flow through the system would be reduced, decreasing cooling efficiency and starving the compressor for lubricant. A clean orifice tube is necessary for a system to operate properly.


Accumulator (found on systems with an orifice tube)

The accumulator catches the liquid refrigerant as it exits the evaporator. The accumulator holds he liquid refrigerant while moisture is removed and the refrigerant turns to a vapor that can be drawn back into the compressor. The lubricant caught in the liquid refrigerant collects at the bottom of the accumulator and is metered into the suction line to be returned to the compressor with the cold refrigerant vapor. The accumulator should be replaced any time the system is open for repair. 


Expansion Valve (if equipped)

The expansion valve drops the pressure and meters the amount of liquid refrigerant flowing to the evaporator in the dash. The temperature of the evaporator determines how much refrigerant is allowed to flow through the expansion valve.


Receiver Drier (found on Expansion Valve systems)

The receiver drier filters, dries and stores the refrigerant in a liquid form until it is needed by the expansion valve. The receiver drier needs to be replaced any time the system is opened for mechanical repairs to remove any trapped debris and to prevent any moisture from forming acids in a system that has been out of refrigerant for a length of time.


Evaporator Core

The evaporator core is located in or near the dash and uses the cold liquid refrigerant released by the orifice tube or expansion valve to absorb the heat in the passenger compartment. It requires that the system be properly charged to work correctly. A system low on refrigerant will starve the evaporator keeping it from cooling the vehicle and moving lubricant on to the compressor.


Gaskets/O-Ring Kit

The system has to have quality seals and gaskets at all connections to contain the pressure of the refrigerant. When the system is opened for repairs, the seals need to be replaced with new ones. 



It is important that the proper amount of clean lubricant circulated in the system at all times. Even a small leak can cause the lubricant  flow to drop in the system. Quality PAG lubricant of the proper viscosity and amount should be put back in the system after repairs have been completed and all contaminated lubricant has been flushed out. This will insure that the new components will perform for an extended period of time. 




A solvent that is compatible with the system including hoses, refrigerant, metals, and o-rings. It is used to clean the evaporator. condenser and hoses after any system failure removing any debris and contaminated lubricant that may be in the system. 


Ice 32

This is a lubricant enhancer that will improve the PAG lubricant's ability to protect the compressor from premature wear and resulting failure. In addition, it increases the heat transfer in both the evaporator and condenser making the system more efficient.



R134a refrigerant systems have very close tolerances for refrigerant charge. An overcharge or undercharge of 2 ounces will effect how well a system will perform. Recharge with the proper amount of refrigerant.

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