Air Conditioning as Standard

The steady growth in air conditioning as a standard vehicle feature meant that Compressortech, the UK & Europe’s leading manufacturer of compressors and condensers, supply the Viper brand. The Viper range includes the UK’s largest range of compressors, as well as a comprehensive range of condensers.

Ideally, the air conditioning system should be used all year round and not just in the summer months. This is because the system ensures that the car’s occupants are provided with clean, filtered air. Yet in reality, this is rarely the case; systems often go unused throughout the winter months, and so, come spring, faults and replacements start to rise exponentially.

System overview
The air con system is a combination of the car heater and a refrigerant circuit. This allows the desired climatic conditions to be maintained, regardless of the outdoor conditions. Components are connected by hoses, forming a closed system in which the refrigerant circulates. The circuit has two sections: the high-pressure side between the compressor and expansion valve (red/yellow), and the low-pressure side between the expansion valve and compressor (blue).


The refrigerant is driven around the system by a compressor. The compression of the refrigerant causes it to become very hot, so the job of the condenser is to cool the refrigerant, causing it to condense and thereby changing its state from a gas to a liquid.
Following this, the filter drier separates impurities and air inclusions from the liquid refrigerant. This protects components from damage resulting from contamination and ensures system effectiveness. The refrigerant now passes to the expansion valve, which acts like a dam, maintaining a uniform pressure in front of the dam. Behind the dam, this pressure is relieved due to the increase in volume. Since the expansion valve is located directly in front of the evaporator, the refrigerant expands into the evaporator. During evaporation, the liquid turns to gas and heat is absorbed from the surroundings.

The evaporator is a heat exchanger similar to the condenser. It has an enormously large surface, over which it can absorb heat from the surroundings for evaporation. This cold air is blown into the vehicle passenger compartment by the ventilation system where it ensures the comfort of the passengers. On the low pressure side the refrigerant is again gaseous, and flows to the compressor where the circuit starts over again.

Why do compressors fail?
A major cause of compressor failure is lack of lubrication. Lubrication is provided by the oil mixing with the refrigerant and flowing through the system. As refrigerant levels drop, the system therefore becomes less and less effective and can ultimately result in compressor failure from oil starvation. As little as a 25% loss of gas charge can start to damage the compressor - each year, up to 10% of the refrigerant is lost from the system through natural seepage. This figure rises once leaks caused by corrosion from salt acid on the road surface, as well as stone chips in the condenser, are taken into consideration.

Another function of the refrigerant is to absorb humidity by trapping moisture in the system’s drier. If the drier becomes saturated condensation forms in the system which can have serious consequences. The excess moisture causes corrosion, increasing wear and mechanical damage to all system components. There is also the possibility that it could freeze, leading to the complete failure of the system. It is therefore important the drier is replaced at regular intervals, before it reaches saturation point, in order to avoid high repair costs.

Another cause of compressor failure is excess high pressure. This can be caused by system blockages, which can cause extremely high-pressure to build up very quickly. This puts undue strain on the unit which can break internal components. High-pressure switches help to protect the compressor but may not be enough to avoid some damage.

Other causes of high pressure are:
• Insufficient condensing of gas
• Cooling fin blockage on condenser/radiator
• Failure of cooling fans, pressure switch or related wiring
• Overcharging the system with refrigerant

The necessary repairs can quickly run up a bill of £700! This can be avoided if the air conditioning system is checked once every 2 years!

Remember!
The air conditioning system is not only used to cool the air, but also condition the air in the passenger cabin for a healthy interior climate. It can also be used to demist the interior of the vehicle, during the cold and wet season when the air is damp and humid. Just turn the air conditioning system on to dry the air and clear the windows quickly to eliminate any safety risks from restricted view.