Volkswagen Golf Service & Repair Manual: Comfort

Volkswagen Golf Service & Repair Manual / Air conditioning system with refrigerant R134a / General notes on air conditioning systems / Comfort

A basic requirement for concentrated and safe driving is the feeling of comfort in the passenger compartment. Especially when it is hot and humid, comfort can be attained only through the use of air conditioning. Of course, open windows, an open sunroof or increased air ventilation can contribute to comfort, but they all have certain disadvantages within the vehicle interior, such as additional noise, draughts, exhaust gases, unfiltered entry of pollen (unpleasant for allergy sufferers).

A well regulated air conditioning system in conjunction with a well thought-out heating and ventilation system can create a feeling of well-being and comfort by regulating the interior temperature, humidity and rate of air change, regardless of the external conditions. This must be available whether the vehicle is moving or not.

Other important advantages of air conditioning are

The cleansing of the air directed into the passenger compartment. (Dust and pollen, for example, are washed out by the moist fins of the evaporator and carried off with the condensation water.)

Temperatures in a mid-range car (for example, after a short period of driving, ambient temperature 30°C in the shade and the vehicle in direct sunlight).

	With air conditioning system	Without air conditioning system
Head region	23°C	42°C
Chest region	24°C	40°C
Footwell	30°C	35°C

Environmental aspects

Since about 1992, the air conditioning systems of newly manufactured cars have been successively changed to refrigerant R134a. This refrigerant contains no chlorine and thus does not damage the ozone layer.

Up until about 1992, air conditioning systems were charged with refrigerant R12. Due to its chlorine atoms, this CFC has a high potential for destroying ozone and, in addition, a potential for increasing the greenhouse effect.

There are programs for exchanging old air conditioning systems containing the ozone-damaging refrigerant R12.

→ Repair manual for air conditioning systems with refrigerant R12. This workshop manual is only available as a hard copy.

To protect the environment, no refrigerant should be released into the atmosphere → Chapter (statutory texts and instructions).

How air conditioning works

The temperature in the passenger compartment depends on the amount of heat radiated through the windows and conducted by the metal parts of the body. In order to maintain comfortable temperatures for the occupants on very warm days, part of the available heat must be pumped away.

Since heat spreads towards cooler bodies, a unit that can create low temperatures is fitted in the vehicle interior. Refrigerant is constantly being evaporated in it. The latent heat of evaporation is taken from the air passing through the evaporator.

The refrigerant carries the heat with it as it is pumped away by the air conditioner compressor. The work performed by the air conditioner compressor on the refrigerant increases its heat content and its temperature. Its temperature is now considerably higher than that of the ambient air.

The hot refrigerant flows with its heat content to the condenser. There the refrigerant looses its heat through the condenser to the surrounding air due to the temperature gradient between the refrigerant and the surrounding air.

Thus, the refrigerant is a means of heat transport. Because it will be needed again, it returns to the evaporator.

All air conditioning systems basically depend on the circulation of refrigerant. However, there are differences in the construction of the system.

Refrigerant machine oil

Refrigerant machine oil is miscible (approx. 20%–40% depending on the type of air conditioner compressor and the quantity of refrigerant) in the refrigerant. I ...

General safety

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