Air-Conditioning System,Switching on the aircon button or climate control activates the compressor, which is attached to the engine & powered by the drive belt.The compressor compresses (& therefore heats) the refrigerant & pumps it through a pipe to the condenser (nearly always mounted directly in front of & looks almost identical to the coolant radiator).
Airflow caused by forward movement of the vehicle, assisted by the radiator fan, passes over & through the condenser, cooling the refrigerant, which is then pumped through to a receiver/drier. This has a filter to trap debris in the system & also contains a drying agent to remove moisture.
The refrigerant then passes to an expansion valve, calibrated to reduce the pressure (& therefore the temperature & flow) of gas so that when it emerges from the valve its temperature will be between 3 & 8 degrees centigrade.From there the cold refrigerant passes through an evaporator, normally situated underneath the vehicleâ€™s dashboard. The blower motor draws air from inside or outside the cabin, over the cold evaporator, which absorbs heat, thus allowing chilled air to pass into the cabin.
The refrigerant is sucked back into the compressor & the cycle starts again.There are variations in the positioning & type of some components used (e.g. on Fords & Audis), but otherwise the layout remains the same on all vehicles.As with a car engine, oil is required to lubricate the moving parts of the compressor. The oil is carried around the system by the refrigerant & pressure switches built into the system act as monitors so that if pressure:
(a) drops too low (e.g. loss of refrigerant) or(b) becomes excessive (e.g. blockage in condenser),A signal is sent to turn off the compressor, preventing damage to it or the system.In-car & exterior temperature sensors are installed to assist efficient operation of the a/c system & ensure a comfortable cabin environment.
Electrics: Engine and a/c control modules constantly monitor the a/c system. If a fault develops(e.g. cooling fan seizes), then the compressor may be de-activated.Some car models have a pollen filter fitted to prevent dirt, dust & pollen from air being drawn into the vehicleâ€™s cabin. As with engine air filters, these need replacing at regular intervals, otherwise they become clogged with dirt & you will have a noticeable lack of airflow into the cabin.
Aware of a bad smell inside the car? This can be caused by a build-up of dirt & thus bacteria on the tubing of the evaporator, especially if no pollen filter is fitted. Aerosol fungicide sprays are available to solve this problem.Notice a pool of clear water underneath the car after using the a/c system, especially on hot & humid days? This is caused by moisture from the warm air in the cabin being drawn over & condensing on the cold evaporator tubing, then dripping out through a drain tube in the bottom of the evaporator casing.This tube can become blocked by debris/bacterial growth & this becomes evident when you suddenly notice that the front passenger footwell has become a miniature paddling pool!