Pic. 12.2. Schematic diagram of the movement of the refrigerant in the air conditioning system: 1 - combined pressure sensor; 2 - section of the high pressure pipeline; 3 - receiver-drier; 4 - service valve of the high pressure line; 5 - condenser (air conditioning radiator); b - fan of the condenser and radiator of the cooling system; 7 - air conditioner compressor; 8 - section of the low pressure pipeline; 9 - service valve of the low pressure line; 10 - heater fan; 11 - evaporator; 12 - thermostatic valve
A schematic diagram of the movement of the refrigerant in the air conditioning system is shown in fig. 12.2.
Compressor (pic. 12.3) piston type mounted on the engine and driven by a V-ribbed belt.
Pic. 12.3. Air conditioning compressor: 1 - pressure disk; 2 - drive pulley; 3 - block of the electrical connector of the electromagnet coil; 4 - plug of the pipeline fastening flange; 5 - cover of the petal valve block; 6 - cylinder block; 7 - plug holes for oil control; 8 - front cover of the case; 9 - clamping plate fastening nut
The compressor circulates the refrigerant in the system. The compressor shaft is mounted in an aluminum housing on two needle bearings and sealed on the side of the drive pulley with an oil seal.
The compressor drive pulley 2 is mounted on a double-row ball bearing and constantly rotates when the engine is running. When the air conditioner is turned on, torque is transmitted from the pulley to the compressor shaft through a friction clutch with an electromagnetic drive.
Notes
If the system is working properly, when the air conditioner is turned on, a click is heard - this is the clutch pressure plate, under the action of an electromagnet, engages with the drive pulley, and the compressor rotor begins to rotate.
But during the operation of the air conditioner, the following compressor malfunctions may occur.
1. If, when the air conditioner is turned off, the clutch makes extraneous sounds during rotation, heats up, or a burning smell appears, then its bearing has probably begun to collapse. In this case, the bearing must be replaced (see «Drive pulley bearing replacement»). In some advanced cases, it may be necessary to replace the compressor clutch assembly or its constituent parts.
2. If you don’t hear a click after turning on the air conditioner, then the following problems are possible:
- there was a refrigerant leak, and the control system blocks the compressor from turning on;
- the pressure sensor in the system has failed;
- malfunctions in the electrical circuits of the control system;
- the coil winding of the clutch electromagnet burned out;
- engine control unit for any reason (high engine coolant temperature, high engine speed) blocked the compressor.
3. If the clutch rotates easily and freely, but when the air conditioner is turned on, extraneous noises are clearly audible or the engine even stalls, then the compressor is most likely stuck. The internal pump part of the compressor cannot be repaired. In this case, the compressor will have to be replaced.
4. And the last, most insidious option. A click is heard, the clutch easily rotates the compressor shaft, and there is no coolness in the cabin. In this case, it only seems that the compressor is working, but in reality it is not pumping anything. Only an experienced specialist with special control and diagnostic equipment can establish the truth.
In all these cases, it is possible to accurately determine the cause of the malfunction after a complete diagnosis at a specialized service center for the repair of automotive air conditioners.
In some versions of the compressor, an emergency pressure relief valve can be installed on the cover 5 of the reed valve block. In the event of an increase in pressure in the system due to a failure of the pressure sensor or other emergency situations, when the set maximum pressure is exceeded, the valve membrane is destroyed and part of the refrigerant is released into the street. As a rule, after this, the tightness of the emergency valve is broken, therefore, after eliminating the causes that caused the pressure increase and refrigerant discharge, the valve must be replaced.
Condenser (air conditioning radiator) multi-flow type is located in front of the radiator of the engine cooling system. It is attached on four brackets to the radiator. The condenser cells are made of flat thin-walled aluminum tubes with internal longitudinal baffles for rigidity and external fins to improve heat transfer. Tanks A and B are aluminum. Receiver B is attached to the left tank. The tanks are divided in height into sections, therefore, passing through the condenser, the refrigerant flow changes direction several times. In the condenser, the vapors of the refrigerant compressed by the compressor are condensed, and the heat released in this case is removed to the surrounding air.
When the air conditioner is turned on, the engine control unit turns on the power supply circuit for the electric radiator fan of the engine cooling system, which improves heat transfer in the condenser and reduces pressure in the air conditioner system.
Helpful Hints
At least once a year, preferably before the start of summer operation, wash the fins A of the condenser honeycombs from adhering dirt, dust and anti-icing agents B. This will improve heat transfer, reduce pressure in the system and increase the service life of the system elements.
Do not use high pressure water jets to clean the condenser. This may cause damage to the B thin-walled fins. Even with regular washing, the need to replace the condenser occurs much more often than we would like. The fact is that he is the first to take on the flow of anti-icing reagents, dirt and pebbles from the road. And his tubes are thin... In most cases, the condenser is damaged by corrosion in the third or fourth year of operation.
If the tightness of the condenser is broken as a result of corrosion, then it is more expensive to repair it. Even if the master of argon welding manages to patch the hole, a leak may soon appear elsewhere. By the way, the pressure in the system on hot days can reach up to 25-28 bar.
In addition, the complex structure of the condenser tube should be taken into account: along it is divided into channels by partitions, so it is highly likely that after welding, some of the channels will be blocked. Accordingly, the dissipated power will drop and the operation of the air conditioner will deteriorate, especially in traffic jams and in hot weather.
After each experiment with condenser patching, you will need to pay for removal-installation, welding of the condenser and charging the system with refrigerant. So it is better to immediately install a new condenser. Instead of an expensive original one, it is quite possible to buy a cheaper condenser from authorized spare parts manufacturers.
Evaporator located in the block of the heating and air conditioning system. The evaporator is made of aluminum tubes with external fins to improve heat transfer. Passing through the evaporator tubes, the boiling refrigerant actively absorbs heat from the air blowing over the outer finned surface of the tubes. The air is cooled and blown into the vehicle interior by a fan.
Note: When the air passing through the evaporator is cooled, the water vapor contained in it condenses.
Condensate drains through a drain pipe located under the lining in front of the central floor tunnel, drains under the bottom of the car. If the ambient humidity is high, a puddle of water may form under the car, which is an indirect sign of the health of the air conditioning system.
Helpful advice: During the operation of the car, particles of road dust and dirt settle on the outer surface of the evaporator that is wet from condensate.
This layer becomes an excellent environment for life and rapid reproduction of putrefactive bacteria and fungal cultures. Over time, an unpleasant odor develops in the car. It is especially strong when the air conditioner is turned off and in humid weather.
In order to minimize the risk of this problem, when buying a new car, it is necessary to carry out preventive treatment of the evaporator with special chemicals, regularly replace the cabin filter and clean the drain tube. If, despite the measures taken, the smell still appears, contact a specialized car air conditioning repair service to disinfect or flush the evaporator. In case of very strong contamination, the evaporator will have to be replaced.
thermostatic valve block type is located in the passenger compartment in the evaporator housing. The valve is attached to the pipelines and the evaporator using flange connections. After passing through the throttling hole in the valve body, the liquid refrigerant abruptly reduces its pressure and begins to boil. A regulating element is installed in the valve body that changes the flow area of the throttling hole depending on the pressure and temperature of the refrigerant. The control element is set at the factory and cannot be adjusted during operation.
Receiver dryer mounted on the condenser on the left side and forms a non-separable unit with it. The filter element is inside the housing (cartridge), filled with desiccant granules (silica gel). The liquefied refrigerant passing through the receiver is cleaned of possible impurities, dirt and moisture. In the lower part of the housing there is a hole for replacing the filter element.
Warning: In case of repair or replacement of air conditioning system components, if it was in the open state (some units were removed, pipelines were destroyed, etc.), the receiver-dryer cartridge must be replaced. Otherwise, after charging the system, the refrigerant will not drain and acids may form inside the system, which will destroy the parts of the air conditioner from the inside.
Pipelines connect all elements of the air conditioning system into a single sealed circuit. Pipelines and their fastening flanges are made of aluminum alloys.
Protect metal sections of pipelines from dents and kinks. Any narrowing of the flow area of the pipeline leads to a decrease in system performance.
To connect the mutually moving elements of the system, pipelines in some sections are equipped with flexible connectors (pic. 12.4) from synthetic materials.
O-rings made of neoprene are installed at the joints of the individual elements of the system. When disconnecting sections of pipelines during the repair of the system, sealing rings must be replaced. Tighten threaded pipe connections to the recommended torque. Weak or excessively strong tightening leads to deformation of the sealing surfaces and refrigerant leakage.
Service valves (two) for connecting diagnostic and filling equipment are located on the pipelines.
Note: This is how the service valves of the high-pressure lines are located on the pipelines...
...and low pressure (The photo shows the valve with the air filter housing removed).
The valves are closed with threaded caps to protect them from dirt. The caps are marked with the letters H and L of the high and low pressure lines, respectively.
The valves are equipped with spools, similar in design to the spools of the wheel tires, but differing from them in size.
A special key is used to turn the spools in and out.
Warning: It is forbidden to check the presence of refrigerant in the system by pressing the spools of the service valves, since after such a check the valve spool may not close completely and the refrigerant will leak from the system!
Pressure meter installed in front of the car in front of the radiator (on its right side) on the pipeline section of the high pressure line. According to the sensor signals, the electronic engine control unit turns off the air conditioning compressor in case of depressurization of the system or an emergency increase in pressure in it in order to protect the compressor from overloads.
Control block the heating and air conditioning system is installed on the instrument panel console. The controls for the heater, air conditioning and ventilation are described in detail R section 1 "Vehicle device», cm. «Heating, air conditioning and interior ventilation».
Note: The passenger compartment temperature sensor is located in the instrument panel (in the heater box). To exclude incorrect readings of temperature values due to the influence of heated panel elements, the sensor is equipped with a forced airflow system. The system provides an even flow of air from the front of the vehicle through the sensor housing. For normal air movement, protect the sensor housing inlet from any solid particles or liquids. This is especially true in cases of dry cleaning of the interior. When cleaning the interior with a vacuum cleaner, it is strictly forbidden to bring the suction tip of the vacuum cleaner pipe to the sensor inlet. If the air flow through the sensor housing is obstructed, the normal functioning of the automatic climate control system is disrupted.
Outdoor temperature sensor located in the front bumper in a sun-protected and ventilated place. However, it is affected by factors such as warm air from the engine and radiation from hot asphalt, so its readings can sometimes be somewhat overestimated, especially after a long period of inactivity in traffic jams. The outdoor temperature readings can be considered correct when driving for at least 10 minutes at a speed of at least 40 km/h.
In a variant to improve the efficiency of the climate control system and more comfortable distribution of air flows in the cabin on the instrument panel (near the windshield glass in the center) can be installed solar light sensor. Depending on the degree of heating of the cabin by the sun, according to the sensor signals, air flows are directed to the area of \u200b\u200bthe face or legs of the driver and front passenger.
refrigerant. An information plate is pasted on the upper surface of the radiator frame indicating the type and volume of refrigerant and oil used in the system. It is strictly forbidden to use other types of refrigerants and oils in the system.
Refueling volumes of the system:
- refrigerant R 134a, kg - 0.65
- PAG oil, ml — 180±5
Notes: During the operation of a car air conditioner, situations periodically arise when maintenance of the air conditioning system or its repair is required. For this, modern diagnostic and repair equipment is used. The most common situation is the depressurization of the system and the release of refrigerant from it.
Highly sensitive halogen leak detectors with sound indication are used to detect leaks.
In some difficult cases, the method of the so-called ultraviolet diagnostics of the tightness of the auto-conditioning system is used.
The method consists in the fact that a special dye is introduced into the system in microdoses. In places of microflows, the dye, together with the refrigerant, gradually comes to the outer surface of the system elements.
During the inspection of the system, the dye begins to glow under the influence of ultraviolet rays of a special lamp (fluoresce)...
...and refrigerant leaks become visible.
It should be noted that the dye does not have any negative effect on the system. It can be in the refrigerant and circulate through the system for an arbitrarily long time and serve its purpose only when a leak occurs.
After repairing the air conditioner, it is necessary to evacuate and charge the system with the appropriate refrigerant (R134a). For high-quality refueling of a car air conditioner, you need:
- precision manometric blocks with special connecting tips;
- two-stage vacuum pump for complete removal of air and water vapor from the system;
- high-precision (division value not more than 5 g) scales for dosing the charged refrigerant.
Due to the specific features of the repair of the air conditioning system, this section describes only the work on the removal and installation of individual elements and the system control unit. Work related to charging the system with refrigerant should be carried out in specialized service centers.
Warning: The air conditioning system is charged with high pressure refrigerant. Contact of liquid refrigerant on human skin causes severe frostbite, so all work related to maintenance, repair or dismantling of air conditioning system elements should be carried out, if possible, in specialized service centers equipped with professional technological equipment. When working on your own, take precautions.