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Function and components of an air conditioning system (Articles) |
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Michael II  10-03-2007, 17:58 |
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Basics of HVAC (Heating, Ventilation, and Air Conditioning) Refrigerant circuit Check pressure (R134a) Diagnosis with VCDS Basics of Air Conditioning Technology Physical Fundamentals: The four known states of aggregation of water also exist in the refrigerants of the air conditioning system. 
1 gaseous (not visible) 2 vaporous 3 liquid 4 solid When water is heated in a container (heat absorption), the rising water vapor is visible. If the vapor absorbs more heat, the visible vapor turns into invisible gas. The process is reversible. If you remove the heat content from gaseous water, it first turns into steam, then into water, and finally into ice.  A- Heat absorption B- Heat release Heat always flows from the warmer substance to the colder substance. Every substance consists of a mass of moving molecules. The rapidly moving molecules of a warmer substance transfer some of their energy to the molecules with less heat and moving slower. This slows down the molecular movement of the warmer substance and accelerates that of the colder substance. This happens until the molecules of both substances move at the same speed. They then have the same temperature, and no further heat exchange occurs. Pressure and boiling point The boiling point of a liquid, as specified in tables, always refers to the atmospheric pressure of 1 bar. If the pressure above a liquid is changed, the boiling point also changes. It is known that, for example, water boils at lower temperatures as the pressure decreases. Based on the vapor pressure curves for water and refrigerant R134a, it can be seen that, for example, at a constant pressure, lowering the temperature causes the vapor to turn into liquid (in the condenser), or that, for example, reducing the pressure causes the refrigerant to transition from liquid.transitions to the vapor state (evaporator).  Water vapor pressure curve A - liquid B - gaseous C - Water vapor pressure curve 1 - Pressure above the liquid in bar (absolute) 2 - Temperature in °C Refrigerant R134a vapor pressure curve A - liquid B - gaseous D - Refrigerant R134a vapor pressure curve 1 - Pressure above the liquid in bar (absolute) 2 - Temperature in °C Vapor pressure table for refrigerant R134a: For each refrigerant, the vapor pressure table is made known in the literature for refrigeration technicians. From this table, it can be determined what vapor pressure is acting on the liquid column in the container, given the temperature of the container. Since a characteristic vapor pressure table exists for each refrigerant, it is possible to determine which refrigerant is present by measuring pressure and temperature. Note! For absolute pressure, 0 bar corresponds to an absolute vacuum. Normal atmospheric pressure (gauge pressure) corresponds to 1 bar absolute pressure. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of one bar (which can be recognized by the indication of -1 bar below 0) .
Refrigerant R134a: The evaporation and condensation process is the method used in air conditioning systems in vehicles. It involves a substance with a low boiling point, which we refer to as a refrigerant. The refrigerant used is Tetrafluoroethane R134a, which boils at -26.5°C under a vapor pressure of 1 bar. Physical data of the refrigerant R134a Chemical formula CH2F-CF3 or CF3-CH2F Chemical name Tetrafluoroethane Boiling point at 1 bar -26.5 °C Freezing point -101.6 °C Criticalische Temperatur 100.6 °C Critical pressure 40.56 bar (absolute) Critical point: The critical point (critical temperature and critical pressure) means that above it, there is no longer a separating surface between liquid and gas. A substance is always in a gaseous state above its critical point. At temperatures below the critical point, all types of refrigerants in pressure vessels have a liquid phase and a gas phase, i.e., there is a gas cushion above the liquid. As long as there is gas remaining in the container in addition to the liquid, the pressure depends on the ambient temperature. þ Page * Vapor pressure table Note Refrigerants must not be mixed with each other. Only the refrigerant specified for the respective air conditioning system may be used. Environmental aspects for the refrigerant R134a R134a is a hydrofluorocarbon (HFC) and does not contain chlorine. R134a has a shorter atmospheric lifetime than the refrigerant R12 R134a does not deplete the ozone layer. The contribution of R134a to the greenhouse effect is 10 times smaller than that of the refrigerant R12.More recent vehicles use R1234yf instead of T134a, which is highly controversial due to the formation of highly toxic substances in the event of a fire. Work is still being done on air conditioning systems that use the harmless CO2 as a refrigerant. Properties of the refrigerant R134a Trade names and designations The refrigerant R134a is currently available under the following trade names: H-FKW 134a SUVA 134a KLEA 134a Note! Due to the wide selection of different refrigerants, only the refrigerant specified for the respective vehicle is permitted for use in motor vehicles.Refrigerants are used. The names Frigen or Freon are trade names. They also apply to refrigerants that are not permitted to be used in motor vehicles. Color Refrigerant, as a vapor and liquid, is colorless like water. Gas is invisible. Only the boundary layer between gas and liquid is visible (liquid level in the riser of the filling cylinder or bubbles in a sight glass). In a sight glass, the liquid of the refrigerant R134a can appear colored (milky). This cloudiness comes from the partially dissolved refrigerant oil and does not indicate a fault. Vapor pressure In a non-fully filled, closed container, refrigerant vapor at the surface evaporates in an amount that, through the joining of vapor particles, returns to liquid. This equilibrium state occurs under pressure and is often called vapor pressure. The vapor pressure is temperature-dependent. Physical properties of R134a The vapor pressure curves of R134a and other refrigerants are sometimes very similar, therefore, a clear distinction based solely on pressure is not possible. The lubrication of the compressor in R 134a systems is achieved using special synthetic refrigerant oils, such as PAG oils (polyalkylene glycol oils). Behavior towards metals In its pure state, refrigerant R134a is chemically stable and does not corrode iron or aluminum. However, impurities in the refrigerant, such as chlorine compounds, can cause certain metals and plastics to be affected.They can be affected. This can lead to blockages, leaks, or deposits on the compressor piston. Critical temperature / critical pressure Up to a gas pressure of 39.5 bar (overpressure, which corresponds to a temperature of 101 °C), the refrigerant R134a remains chemically stable; above this temperature, the refrigerant decomposes (see flammability). Water content Water is only soluble in very small amounts in liquid refrigerant. In contrast, refrigerant vapor and water vapor mix in any proportion. In the refrigerant circuit, any water present is carried along as droplets if the dryer in the liquid or collection container has already absorbed approximately 8 grams of water. This water flows to the nozzle of the expansion valve or the throttle and turns into ice. The air conditioning system stops cooling. Water destroys the air conditioning system because, under high pressures and temperatures, and in combination with other contaminants, acids are formed. Flammability Refrigerant is non-flammable. On the contrary, it has flame-retardant or fire-extinguishing properties. Refrigerant is decomposed by flames and hot surfaces. Refrigerant is also broken down by UV light (which is produced during electric welding). This process creates toxic decomposition products, which must not be inhaled. However, irritation of the mucous membranes will sufficiently and timely warn you. Filling factor In a container, there must be a vapor space adjacent to the liquid space. As the temperature rises, the liquid expands. The space filled with vapor becomes smaller. At a certain point, only liquid will be present in the container. Subsequently, even a slight temperature increase can cause very high pressures to build up inside the container, because the liquid wants to expand further, but there is no more space available. The resulting forces are large enough to rupture the container. To prevent containers from being overfilled, the Pressure Equipment Directive specifies the maximum amount of refrigerant, in kilograms, that can be filled per liter of the container's internal volume. This "filling factor," when multiplied by the internal volume, determines the permissible filling quantity. It is 1.15 kg/l for refrigerants used in vehicles. Detection of leaks The refrigerant circuit can become leaky, for example, due to external damage. The detection of small leaks can be achieved, due to the small amount of refrigerant escaping, for example, using an electronically operated leak detector. This device can detect leaks with less than 5 grams of refrigerant loss per year. (For the different refrigerants, leak detectors must be used that are designed for the composition of the respective refrigerant. For example, Leak detectors for refrigerant R12 are not suitable for R134a, because refrigerant R134a does not contain chlorine atoms, so these leak detectors will not respond. Refrigerant machine oil Refrigerant machine oil mixes (approximately 20-40%, depending on the compressor type and refrigerant quantity) with the refrigerant, constantly circulates in the system, and lubricates the moving parts. In conjunction with R134a air conditioning systems, special synthetic refrigerant machine oils, such as Poly-Alkylene-Glycol (PAG) oil, are used. This is necessary because, for example, mineral oil does not mix with R134a. In addition, the materials of the R134a air conditioning system could be damaged if the mixture flows through the refrigerant circuit under pressure and high temperatures, or if the lubricating film in the compressor breaks down. The use of non-approved oils can lead to the failure of the air conditioning system, therefore only approved oils must be used. Properties of the refrigerant oil The most important properties are high solubility with the refrigerant, good lubricating properties, freedom from acids, and a very low water content. For this reason, only very specific oils may be used; a list of approved refrigerant oils and filling quantities can be found in the vehicle-specific documentation."Repair manual. PAG oils suitable for the refrigerant R134a are highly hygroscopic and not miscible with other oils. Therefore, opened containers should be immediately resealed to protect against moisture ingress." Refrigerant oil degrades due to moisture and acids, becoming dark, viscous, and corrosive to metals. Note! For refrigerant circuits using refrigerant R134a. Only the oil approved for the compressor may be used. Refer to the vehicle-specific repair manual for filling quantities. Due to its chemical properties, the refrigerant oil must not be disposed of together with engine oil or transmission oil. Comfort One of the basic requirements for concentrated and safe driving is the feeling of comfort inside the vehicle. This comfort is only made possible by the use of an air conditioning system, especially at warm temperatures and high humidity. Of course, open windows, an open sunroof, or a higher airflow can also contribute to comfort, but this can lead to disadvantages inside the vehicle, such as: Additional noise, drafts, exhaust fumes, unfiltered entry of pollen and dust (unpleasant for allergy sufferers) A regulated air conditioning system, in combination with a well-designed heating and ventilation system, can create a feeling of well-being and comfort by regulating the interior temperature, humidity, and airflow, according to the external conditions, both when the vehicle is stationary and when it is moving. Environmental aspects {MARK"HE} Since approximately 1992, the air conditioning systems in newly produced automobiles have been successively converted to the refrigerant R134a. This refrigerant contains no chlorine and is therefore ozone-friendly. Until approximately 1992, the air conditioning systems were equipped with the refrigerant R12. This CFC has a high ozone depletion potential due to its chlorine atoms, and additionally, it has the potential to enhance the greenhouse effect. Retrofit programs are offered for existing older systems filled with the ozone-damaging substance R12. For environmental protection reasons, no refrigerants may be released into the atmosphere. How the air conditioning system works The temperature in the passenger compartment..."The temperature inside is determined by radiant heat coming through the windows and by conductive heat transfer through metal parts. However, on very hot days, to create comfortable temperatures for the occupants, a portion of the existing heat must be pumped out. Since heat spreads towards colder temperatures, a unit is installed in the passenger compartment that generates low temperatures. Inside this unit, a refrigerant is continuously evaporated. The heat required for this process is extracted from the air flowing through the evaporator. The refrigerant, with the heat it has absorbed, is then pumped out by the compressor. Due to the compression work performed by the compressor, the heat content and temperature of the refrigerant increase. It is now significantly higher than the temperature of the surrounding air. The high-temperature refrigerant flows towards the condenser, carrying its heat content. There, the refrigerant releases heat to the surrounding air through the condenser due to the temperature difference between the refrigerant and the surrounding air. Therefore, the refrigerant acts as a medium for transporting heat. Since it is needed again, it flows back to the evaporator. For this reason, the fundamental principle of all air conditioning systems is a closed loop for the refrigerant. Differences arise in the composition of the components. Product properties: The refrigerant used in automotive air conditioning systems belongs to the new generation of refrigerants based on chlorine-free, partially fluorinated hydrocarbons (HFCs, R134a). In terms of their physical behavior, these are liquefied refrigerants under pressure. They are subject to the pressure vessel regulations and may only be filled into approved and labeled pressure gas containers. Certain conditions must be met for safe and proper use. Handling of refrigerants.tel! If refrigerant containers are opened, the contents can escape as a liquid or vapor. This process is more intense, the higher the pressure inside the container. The pressure level depends on two conditions: Which type of refrigerant is in the container. The rule is: the lower the boiling point, the higher the pressure. What the temperature is. The rule is: the higher the temperature, the higher the pressure. Do not open containers that contain refrigerants. Wear safety glasses! Put on safety glasses. She prevents refrigerants from coming into contact with the eyes, which could potentially cause severe damage due to freezing. Wear protective gloves and aprons! Refrigerants dissolve fats and oils quite well. Therefore, when they come into contact with the skin, they remove the protective layer of fat. However, skin that has been degreased is sensitive to cold and pathogens. Do not apply liquid refrigerant to the skin! The heat required for evaporation is drawn from the surrounding environment, even if that is the skin. This can result in very low temperatures. The result is localized freezing (boiling point of R134a is -26.5°C at atmospheric pressure). Do not inhale refrigerant vapors in higher concentrations! Refrigerant vapors that escape mix with the ambient air and displace the oxygen necessary for breathing. Absolutely no smoking! Refrigerants can decompose in cigarette embers. The substances produced in this process are toxic and must not be inhaled. Welding and soldering on refrigeration systems! Before welding or soldering on vehicles (near components of the air conditioning system), the refrigerant must be extracted and any remaining residue must be removed by blowing it out with nitrogen. Decomposition products formed from the refrigerant due to heat exposure are not only toxic but also highly corrosive, which can damage pipes and system components. These are essentially hydrogen fluorides. Pungent odor! The presence of a pungent odor indicates that the aforementioned decomposition products have formed. Under all circumstances, it must be avoided to inhale these substances, as this could result in damage to the respiratory system, the lungs, and other organs. Note! Damaged or leaking parts of the air conditioning system must not be repaired by welding or soldering; they should be replaced.euern. When blowing out components with compressed air and nitrogen, always extract the gas mixture exiting the components using appropriate exhaust systems (workshop exhaust system). After completing maintenance work, screw closure caps (with seals) onto all connections with valves and service connections. Start-up of the air conditioning system. Pay attention to filling quantities. Do not refill any refrigerant; extract the existing refrigerant and refill the system. Before starting up the air conditioning system after a new refill: - Manually rotate the compressor approximately 10 revolutions via the coupling or pulley of the magnetic clutch. - Start the motor with the compressor/control valve switched off. - After the motor's idle speed has stabilized, turn on the compressor and operate it for at least 10 minutes at idle speed and maximum cooling capacity. General information about the refrigerant circuit Components of the refrigerant circuit Distribution of the components of the refrigerant circuit and their influence on the high-pressure and low-pressure sides On the high-pressure side, there is the condenser, the liquid receiver, and, as a separation between the high-pressure liquid side and the low-pressure liquid side, the throttling valve or the expansion valve. High pressure is created because the throttling valve or the expansion valve forms a bottleneck, and the refrigerant accumulates, which leads to an increase in pressure and temperature. Too high pressure occurs when there is too much refrigerant, the condenser is dirty, the fan for the radiator is defective, or there is a blockage.fung in the system or moisture in the refrigerant circuit (throttling valve icing) is present. On the low-pressure side are the evaporator, temperature sensor, and a separation between the high-pressure gas side and the low-pressure gas side of the compressor. A pressure drop in the system can be caused by refrigerant leakage, a throttling valve or expansion valve (no restriction), a faulty compressor, or a frozen evaporator. Compressor: The compressor is driven by a V-ribbed belt from thevehicle engine. Compressor with magnetic clutch: An electromagnetic clutch attached to the compressor provides the connection when the air conditioning is turned on.Manufactures pulley and compressor crankshafts. Compressor without magnetic coupling: An overload protection device attached to the compressor pulley trips out the compressor in case of difficult operation and protects the belt drive from overload. The compressor draws refrigerant gas from the evaporator, compresses it, and passes it on to the condenser.  The compressor contains refrigerant oil that is miscible with R134a refrigerant at all temperatures. The factory label indicates which refrigerant the compressor is designed for. A control valve regulates the pressure on the low-pressure side within the specified setpoint range (control characteristic curve). In compressors without a magnetic coupling, a control valve is controlled from the outside. In compressors without a magnetic coupling, the motor should only be started when the refrigerant circuit is completely assembled. To prevent the compressor from being damaged when the refrigerant circuit is empty, the magnetic coupling is deactivated, the control valve N280 is no longer activated, and the compressor runs idle with the motor. In compressors without a magnetic coupling, when the refrigerant circuit is empty, a valve switches to internal lubrication. Overload protection.The overload protection trips the compressor in case of overload and protects the belt drive from overstress. The compressor draws refrigerant gas from the evaporator, compresses it, and passes it on to the condenser. Condenser: The condenser dissipates heat from the compressed refrigerant gas into the ambient air. In the process, refrigerant gas condenses into a liquid. Evaporator:  The liquid refrigerant evaporates in the tubes of the evaporator. The heat required for this is extracted from the air flowing past the evaporator fins. The air cools down. The refrigerant evaporates and is drawn into the compressor along with the absorbed heat.A defined amount of refrigerant is supplied to the evaporator through a throttling valve or expansion valve. In systems with an expansion valve, the flow rate is regulated so that only gaseous refrigerant exits the evaporator. Sight glass:  Not installed in R134a systems, as it is not suitable for R134a. If a sight glass is present in systems that have been retrofitted from R12 to R134a, the mixture of refrigerant R134a and refrigerant oil in the sight glass may appear milky, even though the refrigerant itself is transparent. } Collection vessel:  To ensure that the compressor only draws in gaseous refrigerant, the collection vessel captures the mixtureof steam and gas coming from the evaporator. The gaseous refrigerant is extracted from the steam. Refrigerant oil flowing in the circuit does not remain in the collection vessel because there is an oil suction port. Moisture that has entered the refrigerant circuit during installation is captured by a filter (dryer bag or cartridge) in the vessel. Gaseous refrigerant with oil is drawn into the compressor. Expansion valve: The expansion valve creates a restriction. This restriction reduces the flow and thereby separates the refrigerant circuit into  the high-pressure side and the low-pressure side. Before the restriction, the refrigerant is warm under high pressure. Behind the restriction, therefrigerant is cold under low pressure. Before the restriction, there is a filter to prevent dirt, and behind the restriction, there is a filter to atomize the refrigerant before it enters the evaporator. Arrow A on the restriction points towards the evaporator.After each opening of the circuit, this must be replaced. Liquid container: The liquid container collects the liquid droplets and then continuously feeds them to the expansion valve.til. Feuchtigkeit,  die während der Montage in den Kältemittelkreislauf eingedrungen ist, wird im Flüssigkeitsbehälter durch einen Trockner aufgefangen.Flüssigkeitsbehälter ersetzen, falls der Kältemittelkreislauf längere Zeit offen war und Feuchtigkeit eingedrungen ist. Bei jedem Wechsel des Kältemittels immer auch den Flüssigkeitsbehälter oder Auffangbehälter mitwechseln. Der Trockenbeutel oder die Trockenkartusche ist in einem nicht verschlossenem Flüssigkeitsbehälter nach kurzer Zeit mit Feuchtigkeitgesättigt und unbrauchbar. Expansionsventil: Das Expansionsventil zerstäubt zuströmendes Kältemittel und regelt die Durchflußmenge so, daß der Dampf je nach Wärmetransport erst am Ausgang des Verdampfers gasförmig wird.  O-Ring Dichtungen: Diese Ringe dichten die Verbindungsstellen zwischen den einzelnen  Bauteilen des Kältemittelkreislaufes ab.Es dürfen nur O-Ringe verwendet werden, die beständig gegen Kältemittel R134a und zugehörige Kältemittelöle sind. Grundsätzlich nur einmal verwenden.Vor den Einbauen mit Kältemittelöl benetzen. Rohre und Schläuche des Kältemittelkreislaufes: Das Gemisch aus Kältemittelöl und Kältemittel R134a greift bestimmte Metalle (z.B.Copper) and alloys, and dissolves certain hose materials. The pipes and hoses are held together by screwing or using special connectors. Observe the specified torque values for threaded connections, and use the intended unlocking tools for connectors. Pressure relief valve: The pressure relief valve is mounted on the compressor or liquid container. At a pressure of approximately 38 bar, the valve opens and closes again when the pressure decreases (approximately 30 bar). The refrigerant does not completely drain out. Depending on the design, a transparent plastic disc may be attached. which occurs as soon as the valve responds. Refrigerant circuit with expansion valve and an evaporator.  1- Evaporator 2- Expansion valve 3- Valve for evacuating, filling, and measuring4- Sight glass is not installed in R134a circuits, except for retrofits Circuits5- Liquid receiver with dryer  6- Condenser7- Compressor Note! Arrows indicate the flow direction of the refrigerant. Refrigerant circuit with expansion valve and two evaporators. 1- Evaporator 2- Expansion valve 3- Valve for evacuating, filling, and measuringn4- Sight glass not installed in R134a circuits, except for retrofit circuits5- Liquid receiver with dryer  6- Condenser7- Compressor 8- Refrigerant circuit solenoid valve 9- Expansion valve 10- Second evaporator Refrigerant circuit with throttle and collection vessel. 1- Compressor 2- Condenser 3- Throttle4- Evaporator 5- Collection vessel  Check pressures in the refrigerant circuit (R134a, with service station) and function NoteThe air conditioning system is working correctly if the temperature at the switchboard outlets is aon 7°C or lower outlet temperature. Testing prerequisites: The radiator and condenser are clean (verschandeln if necessary). The thermal insulation on the expansion valve is in good condition and properly mounted. The V-ribbed belt is in good condition and properly tensioned. / The belts for the compressor and three-phase generator are in good condition and properly tensioned. All air ducts, covers, and seals are in good condition and properly mounted. Troubleshooting of the electrical system and the vacuum system did not reveal any errors. The self-diagnosis of the air conditioning system does not indicate any errors; no compressor shut-off condition is displayed in the measurement block (only for vehicles with self-diagnosis)."air conditioner"). The airflow through the dust and pollen filter is not affected by contamination. The air conditioning unit does not draw in any secondary air at the highest fresh air fan speed. The evaporator and the heater do not draw in any secondary air at the highest fresh air fan speed. The air distribution flaps in the air conditioning unit, the heater, and the evaporator reach their end position. * The fresh air intake channels under the front panel and in the passenger compartment, and the associated drain valves, are in good condition. The engine is at operating temperature. The vehicle is not exposed to direct sunlight. The ambient temperature is greater than 15° C. All control panel vents are open. With the engine running and the air conditioning system set to maximum cooling performance: The coolant fan (fans) -V7- runs (at least at level 1). The fresh air blower V2- runs at maximum speed. The recirculation/fresh air flap switches to "recirculation mode" / the back pressure flap closes and the recirculation flap opens (within 1 minute of starting the vehicle). Note In certain configurations, the fan is only activated after the pressure in the refrigerant circuit exceeds a specified value. Ambient temperature in °C Pressure in the refrigerant circuit in bar
of one bar (recognizable by the indication of -1 bar below 0).In vehicles with the high-pressure sensor G65, where the measured pressure is displayed in the measurement value block,the measured pressure corresponds to the actual pressure. The pressure in the refrigerant circuit is lower than specified in the table. Insufficient refrigerant in the circuit. - Check for leaks in the refrigerant circuit using a leak detector. - Check the pressure relief valve. Note! If the pressure relief valve has vented:- Check the fan control for the coolant. - Inspect refrigerant lines and hoses for cross-sectional restrictions due to insufficient bending radii. - Inspect refrigerant lines and hoses for external damage. - If no fault is detected, blow out the refrigerant circuit with compressed air and nitrogen, and replace the filter dryer. The pressure in the refrigerant circuit corresponds to the table or is higher. - Start the engine. - Set the air conditioning to maximum cooling power. Note! If the low-pressure switch was removed to connect the service station, bridge the electrical connections in the corresponding connector for pressure measurement. The compressor is driven by the motor via the magnetic coupling. The control valve N280 for the compressor is controlled by the air conditioning control unit. If the compressor is not driven when the engine is running, or the control valve is not activated: - The cause can be determined, for example, by querying the air conditioning system's error memory.itten and eliminate - Check prerequisites - Check the power supply for the magnetic coupling N25, if it is okay, repair the magnetic coupling. - Check the control of the control valve N280 For vehicles with a throttle and collection tank, check the pressure (with an internally controlled compressor) Note Check prerequisites - Bring the engine speed to 2000/min. - Observe the pressure gauge Note The switching pressures for the switches on the refrigerant circuit are vehicle-specific. The connection with a valve for the low-pressure switch or on the evaporator is only for vehicles without Use the service connection on the low-pressure side and with a non-accessible connection at the compressor or collection tank (measurement accuracy). This applies only to certain vehicles. Target values: High-pressure side: From the initial pressure (when connecting the pressure gauge) to a maximum of 20 bar overpressure, increasing. Low-pressure side: From the initial pressure (when connecting the pressure gauge) to the diagram value, decreasing. A - High pressure (measured at the service connection) in bar overpressure. B - Low pressure (measured at the connection with the valve on the compressor or the collection tank) in bar overpressure. C - Permissible tolerance range. D - LowPressure (measured at the connection with the valve for the low-pressure switch or at the service connection) in bar, overpressure.  E- Permissible tolerance range. Possible deviation from the target value
Possible deviations from the target value Possible causes of error Possible solution The high pressure remains constant or increases only slightly (compared to the pressure with a stationary engine), the low pressure drops quickly to the diagram value or lower, and the required cooling capacity is not achieved. The high pressure is normal, the low pressure corresponds to the diagram value, but the required cooling capacity is not achieved. Insufficient refrigerant in the circuit or expansion valve malfunction.entil defect.  Extract refrigerant from the refrigerant circuit. The amount of refrigerant extracted corresponds to approximately the specified filling quantity => Replace the expansion valve. Refill the refrigerant circuit. Repeat the test.
9.1 The pressure in the refrigerant circuit is lower than specified in the table (insufficient refrigerant in the circuit). Search for leaks using a leak detector. Pressure relief valve is open; check the fan control for the refrigerant according to the wiring diagram. Inspect refrigerant lines and hoses for excessively small bending radii (cross-sectional narrowing) or external damage. If no fault is found, flush the refrigerant circuit and replace the filter dryer. The pressure in the refrigerant circuit corresponds to the table or is higher: Start the motor. Set the air conditioner to maximum cooling power. Open the doors. Outlets in the control panel.open. - The compressor is driven by a V-ribbed belt via the magnetic coupling. powered by the motor. Note: If the compressor is not running, check the voltage supply to the magnetic coupling N25 according to the wiring diagram . If the voltage supply is correct, repair the magnetic coupling.
Possible cause of error PossibleThe solution The high pressure remains constant or increases only slightly (above the pressure with a stationary engine), the low pressure drops quickly to the diagram value or lower, and the required cooling capacity is not achieved. High pressure is normal, low pressure corresponds to the diagram value, but the required cooling capacity is not achieved. High pressure is normal,low pressure is too low (seediagram), and the required cooling capacity is not achieved. Control of the control valve N280 is faulty. There is too little refrigerant in the circuit.  Check the control valve N280 . Search for leaks with a leak detector and eliminate them. Refill the refrigerant circuit, replace the filter dryer . The high pressure only increases slightly above the pressure with the engine stopped, the low pressure only decreases slightly, and
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| Ratings - Function and components of an air conditioning system | |
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