BMW 3 Series E30

since 1983-1994 release

Repair and operation of the car

Being once a prerogative only of smart cars, the conditioner nowadays becomes an integral part of the increasing and bigger number of "ordinary" family cars. By estimates of experts, by the beginning of the next century a half of all European cars will be on sale with the conditioner as a standard accessory.

Air conditioning system, simply speaking, selects heat at air, and also reduces the level of its humidity. Therefore, air in a car interior always more cool and not such damp that creates feeling of freshness.

How the microclimate in salon is created?

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

The most important detail on which overall performance of the conditioner depends is the regulating gate which is installed on the evaporator placed in interior of the car. Coolant in the form of liquid under high pressure comes via the regulating gate to the evaporator where it is sprayed in the form of gas-drop mix (fog). The regulating gate can be needle or like a diaphragm. We will consider the first option.

In the needle gate there is a small opening, and the needle located in an opening is capable to block more or less it, changing thus effective section. The needle is put in action from the thermal sensor placed in the evaporator.

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

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 consumption in the evaporator is not regulated, but its giving is controlled by means of the thermorelay or the relay of pressure. Having turned into gas of low pressure, coolant passes on the evaporator (heat exchanger) and selects heat at air in salon. For bigger efficiency of this process the heat exchanger is supplied with edges. The moisture which is contained in air is condensed on the external surface of the heat exchanger and merges out of salon. Air, having passed through the heat exchanger, comes back to salon colder and dry.

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

The compressor which problem – to banish coolant on system tubes, transferring heat from low temperature level to higher, works by the principle of the pump and is given by a belt from the engine via the electromagnetic coupling that the conditioner could be switched-off. When the compressor works, it creates depression which "exhausts" gaseous coolant from the evaporator.

In the compressor pressure of coolant increases, and it comes to the condenser, but already in the form of gas under high pressure. In the condenser gas turns into liquid again, at the same time heat which is contained in it dissipates from the surface of the condenser in the atmosphere.

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

Additional "lotions"

In practice the described basic scheme includes still some knots, in particular, a receiver dehumidifier which often (but not always) is mounted between the condenser and the regulating gate. This device (it sometimes call "accumulator") filters coolant and deletes from it moisture. Sometimes the dehumidifier is supplied with the color indicator which shows when it is time to replace its (it means that it gathered a moisture maximum). (Between the condenser and the evaporator) sometimes build in viewing glass system of tubes, and then it is possible to watch a condition of coolant (existence of unnecessary bubbles etc.).

Enter air conditioning system also the supercharger banishing air via the evaporator, and the fan with the thermostat increasing overall performance of the condenser. Usually is a part of the system also pressure sensor with the switch. It is located near a receiver dehumidifier and operates operation of the compressor and fan of the condenser, and also supports optimum pressure in system (a miscellaneous for different systems).

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

And how with ecology?

Until recently in automobile conditioners R12 freon was applied. Then it was established that the chlorfluorocarbons which are contained in it perniciously influence an ozone layer therefore now it is forbidden to release R12 in the atmosphere. Besides, under the influence of an open flame of R12 phosgene emits deadly gas. It is still authorized to fill with it conditioners of former releases as also operation of these conditioners is allowed.

Respectively, the price of R12 freon raises by 5–10% a month. Eventually it will become such that will begin "to recharge" old systems is simply ruinous. Already now R12 freon stands up in the west of $150 for kilogram, and cost $65 two years ago. In modern systems more "eco-friendly" coolant – R134A is used.

The systems calculated on R134A are arranged so that at service and repair there were no leaks. For this purpose in the right places special valves and other devices are installed.

Theoretically, R134A can be downloaded also in the old conditioner, having made corresponding changes. However, this coolant of percent 15 is less effective, than R12 therefore the conditioner of old type will work with it worse. Besides, there is one more problem: R134A coolant filters, though is weak, through the hoses made of pure rubber. Special hoses with an internal nylon braid are necessary for this substance. At the same time in old systems so-called "zayershenny" connecting unions which are capable to break through this braid are used. In a word, it is at the moment more favorable to use old coolant.

Generally, there are so-called "replaceable" coolants intended for replacement of R12 and which are not demanding expensive alteration of system for R134A, but as experts speak them it is impossible and to admit 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 want to pass from R12 to R134A, then it is the best of all to change together with coolant oil (mineral for synthetic) in system, to establish a new receiver dehumidifier, to replace rubber hoses and to check work of all knots. Then there is a hope that the system will well work.

That everything worked

In order that air conditioning system well worked, it is necessary to be able to handle it. For example, many do not know that the conditioner will only work then effectively when in the car all windows, and also the hatch are closed. Quicker to cool salon in very hot day, it is necessary for a minute - another to open all doors and when blows the car – to close everything and to turn on the conditioner (at the working engine).

The draining influence of the conditioner reduces fogging wind and side glasses of salon therefore sometimes it is useful to turn on the conditioner along with an oven. However, some climatic systems do not provide simultaneous operation of the conditioner and an oven.

In air conditioning system there is an oil which circulates together with coolant. If the system long stays idle, some of its details, in particular, neoprene laying, dry up and collapse, leaking. Therefore it is desirable to turn on once a week the conditioner not less, than for ten minutes including in the winter that oil greased all knots of system.

What can be repaired?

Conditioners are not subject to "house", amateur repair. Coolant – substance whimsical, for its full pumping and downloading new is required the professional equipment and to provide full tightness, special highly sensitive devices for identification of leaks are necessary.

If the conditioner broke, so at least, some details need to be replaced, including special tubes and a fitting, but there is a set of their standard sizes. And special blooming devices are used to fastening of tubes to a fitting.

So if you had problems with the conditioner, rely only on experts. Address to firms which make complex repair, and not just pump the disappeared coolant. If coolant "left" system, then in the beginning it is necessary to find the reason, otherwise new coolant will disappear in the same way!

Similarly, if at you jammed the compressor, then it is simple to replace it insufficiently: in several months will jam it again. It is necessary to remove from system shaving and other garbage in the beginning, and then to wash out it special solution or nitrogen. It is also necessary to replace a receiver dehumidifier (in it there was a shaving) and to pump fresh coolant.

Most often the condenser sustains damage. It is located before an automobile radiator and protected only by a radiator lattice.

The second problem is the failure of the needle gate (he is killed with dirt). Cleaning the gate, it is necessary to remove from it dirt, but not to push it inside!

There are also other problems – for example, the compressor rustles. Usually, it speaks about its close end.

It is easy to check a condition of a driving belt. The compressor is given in some cars by a separate belt. It is successful option. However modern cars are often equipped with a long "multipurpose" belt which sets in motion several devices, often at once, including, and the water pump. So if the bearing of the leading pulley of the compressor of the conditioner suddenly jams, you will not leave anywhere, will not find a belt of the smaller size yet "to bypass" the compressor!

Other aspects

If after all there was a leak of coolant through rubber hoses, then their replacement is quite problematic as it is difficult reliable to seal new hoses on an old aluminum fitting.

Keep in mind that the conditioner can not turn on if surrounding temperature is lower set or if pressure in system is much lower (coolant leak) or above optimum.

To violations in operation of the conditioner bring also excess of oil, coolant, hit into system of air or moisture, strong pollution of edges of the condenser or evaporator, malfunction of the cooling system of the car (overheat), and also slipping of the coupling of the compressor.