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  1. Leaks are undoubtedly the most common problem associated with automotive air conditioning systems. Fortunately, they're also the easiest kind of problem to fix.

    1.- Loose fittings or connections: If a minor leak is traced to a connection, the fitting has probably loosened up from vibration. Try tightening it. After tightening a fitting or connection, always check it again for leakage to make sure the problem is solved.

    2.- Deteriorated O-ring seals or gaskets: If tightening a leaky connection doesn't stop the leak, the fitting O-ring seals or gaskets are probably deteriorated (Though it's possible that the fitting itself is faulty or damaged). Discharge the system and disconnect the fittings at the leaky connection. Be sure to clean the area around the fittings before disconnecting them to prevent dirt or grit from entering the system. Use two wrenches when loosening or tightening fittings to avoid kinking the metal refrigerant lines. If the fittings appear to be in good shape, you can probably get by with the replacement of the O-ring seals or gaskets. Perform a leak test to check your work whe the system is reassembled. If the connection still leaks, it's either faulty or damaged. Replace the hose, or hoses, of which it is a part.

    3.- Faulty, porous or worn out hoses: If the leak is due to a defective hose, or the fittings or either end of a hose, it must be replaced.

    4.- Suction throttling valve (STV): if the leak is traced to the Suction Throttling Valve (STV), the problem is probably a torn diaphragm. Older STV uinits have an adjustable, replaceable diaphragm. Later Pilot Operated Absolute (POA) type STVs don't have a repace diaphragm. They must be replaced with a new unit.

    5.- Compressor seal Leak: If the leak is at compressor seal, the compressor must be rebuilt or replaced. Because the large number of compressors in use on various systems and because of the large number of highly specialized, and different, tools necessary to rebuild each compressor, we recommend to exchange the old compressor for a new unit.

    How to check Compressor Leaks

    Source: Haynes Techbook. Automotive heating & air conditioning. By Mike Stubblefield and John Haynes 2009

  2. An important component in the cooling action of the evaporator is the blower motor/fan (usually the same one that blows air through the heater core), also located in the evaporator housing. The blower draws warm air from the passenger compartment over the evaporator and blows the "cooled" air out into the passenger area. The blower motor is controlled by a fan switch with settings from Low to High

    Blower Motor Air Conditioning

     

    Blower Motor

     

    Blower Weel

     

    High blower speed will provide the greatest volume circulated air. A reduction in speed will decrease the air volume. But the slower speed of the circulated air will allow the air to remain in contact with the fins and coils of the evaporator for a longer period of time. The result is more heat transfer to the cooler refrigerant. Therefore, the coldest air temperature from the evaporator is obtained when the blower is operated at its slowest speed. The next section examines various typical controls and describes how they make air conditioning more efficient.

    Source: Haynes Techbook. Automotive heating & air conditioning. By Mike Stubblefield and John Haynes 2009

  3. How to make sure if the system is fully charged?

    Once the system is stabilized, it's ready for testing. There is however, one more thing you must do before starting: make sure the system is fully charged:

    1.- Using a thermometer, measure "ambient" air temperature about two (2) inches in front of the condenser. System pressures are directly affected by the ambient temperature. Jot down your reading and compare it to the ambient temperature column on the accompanying chart showing the relationship between pressure and temperature.

    2.- Insert thermometer into the air conditioning outlet nearest the evaporator. Turn the blower switch to Low and note the indicated outlet air temperature. Again, jot down your reading and compare it to the evaporator temperature column on the accompanying chart.

    3.- Note the high and low side gauge readings and jot them down too. Then compare the preliminary readings to the columns for low and high side pressures, respectively, on the chart.

    4.- If the system is equipped with a sight glass, inspect the refrigerant flowing past the window. If there are some bubbles in the window, the system refrigerant level is low or there is small leak in the system. If the sight glass is clear or oil-streaked, the system refrigerant is excessively low or there is a major leak.

    Relationship between pressure and temperature

    Pressure and Temperature

    Thermometer testing on the closest outlet to the evaporator

    Thermometer

    Source: Haynes Techbook. Automotive heating and Air conditioning by Mike Stubblefield and John Haynes. 2009.

  4.  

    Manifold Gauge Set

    The manifold gauge set is unquestionably the most important tool used in air conditioning system servicing. Nearly all service work performed on automotive air conditioning systems requires the use of test gauges. Test gauges enable a technician to determine the system's high pressure side and low side vacuum, determine the correct refrigerant charge, perform diagnosis procedures and help determine wheter the system is operating efficiently.

    Because pressures must be compared in order to determine how the system is operating, the gauge set is designed to allow both the high and low sides to be read at the same time.



    Manifold Gauge Set

    The "Low side" gauge:

    The low side gauge, which is most easily identified by the BLUE houseing and hand valve, is used to measure the low side pressure at the service ports provided on the low side of the system by the manufacturer. The low side gauge is sometimes called a compound gauge because it has a dual purpose - to indicate either pressure or vacuum.

    The "high side" gauge:

    The high side gauge, which usually has a RED housing and hand valve, is strictly a pressure gauge. It reads from 0 to 500 psi in clockwise direction.

    Auxiliary gauge

    An auxiliary gauge may be required for testing older chrysler vehicles with evaporator pressure regulator (EPR) valves or Fords with pilot operated absolute (POA) valves. It can be either a separate gauge used in conjunction with a two-gauge set or an integral gauge in a three-gauge set.

    Source: Haynes Techbook. Automotive heating and Air conditioning by Mike Stubblefield and John Haynes. 2009.

  5. System using R-134a are similar in appearance and function to system using R-12. Although the use physically larger, heavier duty compressors, condensers and evaporators, cycling clutch, orifice tubes, pressure switches, receiver-driers, etc - are virtually identical to the parts used on R-12 systems. They're not interchangeable Installing a component designed for an R-12 system in a system built to use R-134a - or vice-versa - may cause component failure and could damage the system.

    In 1991, Saab introduced a 1992 model as the first vehicle to use an air conditioning system designed for R-134a. In 1992, Chrysler, Ford, GM, Infiniti, Mercedes, Nissan, Saab and Volvo debuted models using R-134a. By 1993, most vehicles were equipped with R134a systems.

    If you're working on a 1992 or newer vehicle, always determine whether uses R-12 or R-134a before servicing or troubleshooting it. How so you know whether the system in your vehicle uses R-12 OR r-134a? Look for special identification decals or labels on the major components.For instance, some 1992 and later FORD Taurus models with a 3.0L engine use and R-134a system. Ford distinguishes these models with a special yellow tag that says "R-134a NON-CFC" on it. These models also have a gold colored compressor, and green colored O-rings are used throughout the system.



    o-ring

    The high side and low side service fittings on an R-134a system are completely different from those used on an R-12 system. On an R-12 system, the high side service fitting is a 3/8 inch 24 for screw-on couplers; the low side fitting is a 7/16 inch 20. On a R-134a systems, the high side and low side fittings are special 1/2 inch Acme-type fittings with no external threads. They have internal threads but they are for the specially-designed caps unique to R-134a systems; the low side service valve uses a special quick-release service coupler that's also unique to a R-134a systems. And the valve cores on both fittings are also unique to the R-134a systems. In other words, there's no possibility of confusing these fittings with those used on earlier R-12 systems.

    Source: Haynes Techbook. Automotive heating and Air conditioning by Mike Stubblefield and John Haynes. 2009.

  6. Any time more than 1/2-pound of refrigerant is required to charge the system over a period of a year, a leak is indicated. Leakage is the usual cause for low refrigerant charge. Most leaks are caused by normal engine vibration, which loosens threaded fittings and even causes metal lines to fatigue and crack over a period of time. Tighting all the fittings usually eliminates most leaks. Repair or replacement is necessary to cure leaks caused by metal fatigue and cracks.

    How to find a leak witha bubble detector:

    • 1.- Simply apply a commercial bubble detector solution, or even a soap and water solution, to the suspected leak with a small brush. Apply the solution to all fittings and connections where the leak might be.
    • 2.- Start the engine, turn on the air conditioning system and let the presures stabilize.
    • 3.- The leaking refrigerant will cause the detector or soapy solution to form bubbles.
    • 4.- Tighten the loose fitting or repair the leaking components.
    • 5.- Wipe off ther solution and repeat the above procedure to ensure that the leak is fixed.



    leaks air conditioning

    Source: Haynes Techbook. Automotive heating and Air conditioning by Mike Stubblefield and John Haynes. 2009.

  7. There are two basic types of vehicle air conditioning systems. In a typical vehicle air conditioning system, high pressure liquid refrigerant in the condenser is released into the evaporator, via a device, which decreases the refrigerant pressure. The type of device used to decrease the refrigerant pressure give us the basic difference between the type of air conditionig system. it might be either an Expansion Valve or an Orifice Tube.

    Expansion Valves



    Expansion Valves

    Orifice Tubes



    Orifice tubes



    Air conditioning system using an expansion valve

    Components used in this type of systems are:

     

    • 2.- Condenser

    • 3.- Receiver-Drier

    • 4.- Expansion Valve

    • 5.- Evaporator

     

    The compressor compresses the refrigerant from a low-pressure vapor to high-pressure vapor. The high pressure vapor is pumped into the condenser, where its condensed by the cooling airflow to a high-pressure liquid. The high-pressure liquid is pumped to the receiver-drier, where it's cleaned and all moisture is removed. The clean, dry high-pressure liquid is pumped to the expansion valve, where its changed to a low-pressure mixture of liquid and vapor. The low-pressure refrigerant mixture is then pumped to the evaporator, where the remaining liquid is turned back to a low-pressure vapor, cooling the air passing over the evaporator as it does so. From the evaporator, the low-pressure vapor passes back to the compressor, which pumps it through the system again.

    Air conditioning system using an orifice tube

    Components used in this type of systems are:

     

    • 2.- Condenser

    • 3.- Accumulator

    • 4.- Orifice tube

    • 5.- Evaporator

     

    The compressor compresses the refrigerant from a low-pressure vapor to high-pressure vapor. The high pressure vapor is pumped into the condenser, where its condensed by the cooling airflow to a high-pressure liquid. The high-pressure liquid is pumped to the orifice tube, where the flow is restricted. Changing the refrigerant to a low-pressure liquid. The low-pressure liquid is then pumped to the evaporator, where the liquid is partly converted to a vapor, cooling the air passing over the evaporator as it does so. From the evaporator, the low-pressure mixture is pumped to the accumulator, where the remaining liquid is boiled back to vapor. The pure low pressure vapor passes passes back to the compressor, which pumps it through the system again.

    Source: Haynes Techbook. Automotive heating & Air conditioning. By Mike Stubblefield and John Haynes.

  8. Once the system has been opened up for repairs or components replacements, it must be evacuated with a vacuum pump to remove all traces of moisture

    Any amount of moisture is very harmful to air conditioning systems. Moisture reacts with refrigerant to form hydrochloric acid, which damages the system's internal components. That's why every system is equipped with either a receiver-drier or an accumulator to trap and retain the moisture that invariably infiltrates the system.

    Moisture can collect and freeze in the orifice of the expansion valve, restricting the flow of refrigerant. It can do the same thing in a system equipped with a suction throttling valve (STV) or evaporator pressure regulator (EPR) valve.

    Moisture must be prevented from entering the system. Once it gets in, the desiccant in thereceiver-drier or an accumulator is the system's only means of removing it.

    Source: Haynes Techbook. Automotive Heating and Air Conditioning. by Mike Stubblefield and John H Haynes.

  9.  

    If the system provides no cooling air:

     

    1. 1.- Inspect the compressor drivebelt. Make sure it's not loose or broken.
    2. 2.- Check for a blown fuse.
    3. 3.- Check the system wire harness for a blown fusible link.
    4. 4.- Inspect the wire harness for a broken or disconnected wire.
    5. 5.- Inspect the wire harness for a broken or disconnected ground wire.
    6. 6.- Inspect the clutch coil or solenoid. Make sure that neither is burned our or disconnected.
    7. 7.- Make sure the electrical switch contacts in the thermostat are not burned excessively and that the sensing element is not defective.
    8. 8.- Make sure the blower motor is not disconnected or burned out.
    9. 9.- Check the ignition switch ground and realy. Make sure they're not burned out.
    10. 10.- Make sure the compressor isn't partially or completely frozen.
    11. 11.- Inspect the refrigerant lines for leaks.
    12. 12.- Check components for leaks.
    13. 13.- Inspect the receiver drier/accumulator or expansion valve for clogged screens.
    14. 14.- Inspect the compressor shaft seal for leaks.
    15. 15.- If there's hot water in the heater and hot discharge air from the evaporator, the heater valve is inoperative.

    Source: Haynes Techbook. Automotive heating and Air conditioning by Mike Stubblefield and John Haynes. 2009.

  10. <p>Automotive Air conditioning is the process by which air is cooled, cleaned and dehumidified before entering, or re-entering, the passenger compartment. Basically, an air conditioning system removes heat from the passenger compartment by asorbing it and carrying it outside, where it is released into the atmosphere.</p>
    <p>This process is possible because we have learned how to manipulate three simple natural phenomena:</p>
    <ul>
    <li><strong>Heat Transfer:</strong> <br />
    <p>If two materials of different temperatures are placed near each other, the heat in the warmer material will always travel to the colder material until both are the same temperature.</p>
    </li>
    <li><strong>The latent heat of vaporation:</strong> <br />
    <p>When a liquid boils, it absorbs heat without raising the temperature of the resulting gas. When the gas condenses, it gives off heat without lowering the temperature of the resulting liquid.</p>
    </li>
    <li><strong>the effect of pressure on boiling or condensation: </strong><br />
    <p>The saturation temperature of a liquid or a vapor increases or decreases in accordance with the pressure to which it is subjected.</p>
    </li>
    </ul>
    <p><strong>Source: Haynes Techbook. Automotive heating &amp; air conditioning. By Mike Stubblefield and John Haynes 2009</strong></p>