Audi 100/A6

1990-1997 of release

Repair and car operation

14.9.1. As the conditioner works

THE GENERAL DATA

The standard central air consists of the several working knots connected among themselves by tight system of tubes. It is filled by a coolant which passes from the liquid form in gaseous and back, transferring heat from salon.

The most important detail on which the conditioner overall performance depends, the regulating gate which is established on the evaporator placed in salon of the car is. The coolant in the form of a liquid under a high pressure arrives through regulating gate in the evaporator where it is sprayed in the form of a gazo-drop mix (fog). The regulating gate can be needle or diaphragm type. We will consider the first variant.

In the needle gate there is a small aperture, and the needle located in an aperture is capable more or to block less it, changing thus effective section. The needle is put in action from a temperature-sensitive element placed in the evaporator.

Liquid coolant, passing through a small aperture in the gate, evaporates and turns to gas under low pressure. This process is accompanied by sharp temperature drop. The aperture less, the becomes colder халадагент, that is the temperature in the evaporator can be regulated, entering or deducing a needle from an aperture. The temperature of a surface of the evaporator should be close to a water freezing point, but not below it, differently on the evaporator ice that will complicate movement of air and transfer of heat to a coolant will be formed.

As it was already told, instead of the needle gate sometimes, the diaphragm is established. In it there are no moving parts, therefore the coolant expense in the evaporator is not regulated, but its giving is supervised by means of the thermorelay or the pressure relay. Having turned to gas of low pressure, the coolant passes on the evaporator (heat exchanger) and selects heat at air in salon. For большей efficiency of this process the heat exchanger is supplied by edges. The moisture containing in air is condensed on an external surface of the heat exchanger and merges out of salon. Air, having passed through the heat exchanger, comes back in salon colder and dry.

Saved up by a coolant it is warmly necessary to give to atmosphere, for what the coolant by means of the compressor goes to the condenser (is one more heat exchanger located usually in a forward part of the car).

The compressor, which problem – to banish a coolant on system tubes, transferring heat from low temperature level on higher, works by a principle of the pump and is resulted by a belt from the engine through electromagnetic муфту that the conditioner could be disconnected. When the compressor works, he creates depression which "exhausts" a gaseous coolant from the evaporator.

In the compressor pressure of a coolant raises, and it arrives in the condenser, but already in the form of gas under a high pressure. In the condenser gas turns again to a liquid, heat thus containing in it dissipates from a condenser surface in atmosphere.

From the condenser the coolant – already in the form of a liquid under pressure – again moves on regulating gate, and the cycle repeats.

Additional "lotions"

In practice the described base scheme includes still some knots, in particular, a receiver-dehumidifier, which is frequent (but not always) is mounted between the condenser and the regulating gate. This device (it sometimes name "accumulator") filters a coolant and deletes from it a moisture. Sometimes the dehumidifier is supplied with the colour indicator which shows when it it it is time to replace it (it means that it has typed a moisture maximum). System of tubes (between the condenser and the evaporator) sometimes build in viewing glass and then it is possible to observe of a coolant condition (presence of unnecessary vials etc.).

The supercharger banishing air through the evaporator, and the fan enter into a central air with the thermostat, raising a condenser overall performance also. Usually the system includes also the gauge of pressure with the switch. It is located near to a receiver-dehumidifier and operates work of the compressor and the condenser fan, and also supports optimum pressure in system (a miscellaneous for different systems).

In the majority of systems over the evaporator fastens also a heating element. The stream of air with the help "mixing заслонки" is distributed between the evaporator and a heater so that to give it desirable temperature.

And how with ecology?

Until recently in automobile conditioners freon R12 was applied. It has been then established that containing in it хлорфторуглероды perniciously influence an ozone layer, therefore now to let out R12 in atmosphere it is forbidden. Besides, under the influence of open flame R12 allocates deadly gas phosgene. For the present it is authorised to fill with it conditioners of former releases as operation of these conditioners is authorised also.

Accordingly, the price for freon R12 raises on 5–10 % a month. Eventually it becomes such what to "recharge" old systems begins is simply ruinous. Already now freon R12 costs in the West $150 for kg, and two years ago cost $65. In modern systems more "harmless" coolant – R134А is used.

The systems calculated on R134A, are arranged so that at service and repair there were no leaks. For this purpose in proper places special valves and other adaptations are established.

Theoretically, R134А it is possible закачать and in the old conditioner, having brought respective alterations. However, this coolant of percent on 15 is less effective, than R12, therefore the conditioner of old type with it will work worse. Besides, there is one more problem: coolant R134А filters, though and is weak, through the hoses made of pure rubber. Special hoses are necessary for this substance with an internal nylon braid. At the same time in old systems are applied so-called "заершенные" connecting unions which are capable to break through this braid. In a word, it is at present more favourable to use an old coolant.

Generally, there are the so-called "replaceable" coolants which are intended for replacement R12 and not demanding expensive alteration of system on R134А, but as experts speak, it is impossible and to admit them on a gun shot to the conditioner. Some of these substances contain butane which can ignite in system, besides, it will ruin the test equipment.

If you wish to pass with R12 on R134А, is better to change together with a coolant oil (mineral on synthetic) in system to establish a new receiver-dehumidifier to replace rubber hoses and to check up work of all knots. Then there is a hope that the system will work well.