The air conditioning (A/C) system is extremely useful, especially in Australia’s hot climate. While we may think of it as a system that blows cold air into the cabin, it is a little more complicated than that – as the name suggest, it actually ‘conditions’ the air, creating not only cold air, but dry air too.
The system works on the principles of thermodynamics – using evaporation, condensation, compression and expansion to change the state of the refrigerant and remove moisture and heat from the air, resulting in the cold, refreshing breeze flowing into the cabin.
The A/C system comprises of various components that employ these principles. These components are located throughout the engine bay of a car – from a condenser at the very front of the engine bay to an evaporator behind the dash assembly – that are all linked together by a series of hoses and tubes.
- Refrigerant
The liquid/gas used as the ‘active’ ingredient in the A/C system. It is used to absorb heat from surrounding air and changes in composition from gas to liquid at various points in the process.
- Compressor
The compressor is at the heart of the A/C system. It is the ‘pump’ that pressurises and circulates the refrigerant through the system. The compressor is powered by a drive belt that is connected to the engine crankshaft. A clutch system is used to engage and disengage the compressor (so the A/C can be turned on and off) when the engine is running.
- Condenser
The condenser converts the high-pressure gas refrigerant into a liquid. It is similar to a radiator and cool air flows around it removing heat from the refrigerant inside. Removing heat from the gas changes its state from vapour to liquid.
- Receiver
The liquid refrigerant flows to the receiver, a component that removes moisture from the refrigerant.
- Expansion valve
The expansion valve is the point at which the high-pressure system becomes a low-pressure system. The valve allows the pressurized refrigerant to expand, at which point it converts back to a gaseous state. At this point, the refrigerant is extremely cold.
- Evaporator
The evaporator resembles a small radiator and is located behind the dash near the cabin. Cold, low-pressure refrigerant flows through the evaporator and a blower fan pushes air across it. The refrigerant in the evaporator works to absorb the heat and remove moisture from this air and the result is a cold, dry breeze flowing into the cabin. The refrigerant is then moved back to the compressor at which point the process starts again.
The A/C is set up as a closed-loop system and one that is in good working order will ensure the refrigerant stays in place and will be continuously cycled through the system. However, as with all things, over time the components such as hoses, or any of the parts mentioned above, can become loose, crack, or deteriorate to a such a degree that leaks occur and the refrigerant escapes. At this point, the A/C will stop working properly and repair, maintenance and regassing (refilling the refrigerant), performed by a qualified technician, will be required.
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3 December 2019
Please note the information contained on this page is general in nature and does not take into account your specific needs or circumstances. You should consider whether the information is appropriate to your needs, and where appropriate, seek professional advice.