Chris Bede

Today, when we drive a car, many of us can enjoy the same level of comfort that we are used to at home and at work. Just press the button or slide the lever, we can seamlessly switch from heating to cooling, and then switch back, regardless of how this change happened. That is to say, unless something goes wrong.

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Since the automobile air conditioning system of 1940 came out, many things have changed greatly. Such as computerized automatic temperature control (which allows you to set the desired temperature and let the system adjust automatically) and the improvement of overall durability, which increases the complexity of today's modern air conditioning system. Unfortunately, the days of "doing it yourself" to repair these systems are almost over.

To make matters worse, we now have strict environmental regulations to manage the simplest tasks, such as filling the system with refrigerant R 12, which is usually called Freon. (Freon is the trade name of refrigerant R- 12, manufactured by DuPont). Extensive scientific research has proved the destructive effect of this refrigerant on the ozone layer. The United States and many other countries have banned the production of this refrigerant. These countries have jointly signed the Montreal Protocol, a landmark agreement, which was launched in the1980s to restrict the production and use of chemicals known to deplete the ozone layer.

Now, your car mechanic is more subject to this new environmental legislation than ever before. Not only does he need to be certified to buy refrigerants and repair air conditioners, but his shop must also bear the cost of purchasing expensive special equipment to ensure that these ozone-depleting chemicals are captured when the system is opened for maintenance. In short, if your mechanic has to spend more money to repair your car, he will have to charge you more. The basic knowledge of air conditioning system is very important, because it will make you make a more informed decision on maintenance selection.

If there is a big problem with your air conditioner, you may encounter new terms. Words like "renovation" and "alternative refrigerants" have now appeared in your mechanical glossary. You can choose "refitting" instead of just repairing and replenishing Freon. Retrofitting includes making necessary changes to your system, which will allow it to use the new industry-recognized "environment-friendly" refrigerant R- 134a. This new refrigerant has a higher working pressure, so depending on its service life, your system may need larger or stronger components to offset its inherent high pressure characteristics. In some cases, this will greatly increase the final cost of maintenance. And if it is not properly implemented, it may reduce the cooling efficiency, which is equivalent to higher operating costs and reduced comfort.

It is found that there are mainly three different types of air conditioning systems for automobiles. Although these three types are different, their concepts and designs are very similar. The most common components that make up these automotive systems are as follows:

Compressor, condenser, evaporator, throttle pipe, thermal expansion valve, liquid storage dryer, accumulator. Note: If your car has a nozzle tube, it will not have a thermal expansion valve, because these two devices serve the same purpose. Besides, you have either a dryer or a battery, but not both.

For more information about air conditioning, please check the car air conditioning information server.

compressor

The compressor, usually called the heart of the system, is a belt-driven pump fixed on the engine. It is responsible for compressing and conveying refrigerant gas.

The air conditioning system is divided into two sides, high pressure side and low pressure side; Defined as discharge and inhalation. Since the compressor is basically a pump, it must have an intake side and an exhaust side. The suction side sucks refrigerant gas from the outlet of the evaporator. In some cases, it is realized by an accumulator.

Once the refrigerant is sucked into the suction side, it is compressed and sent to the condenser, where the heat absorbed from the car is transferred.

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capacitor

This is the area where heat dissipation occurs. In many cases, the appearance of condenser is very similar to that of radiator in automobile, because their functions are very similar. The condenser is used to dissipate heat. Its position is usually in front of the radiator, but in some cases, its position may be different due to the aerodynamic improvement of the car body. When the system is running, the condenser must have good airflow. In rear-wheel drive vehicles, this is usually achieved by using the cooling fan of the existing engine. On front-wheel drive vehicles, the condenser airflow is supplemented by one or more electric cooling fans.

When hot compressed gases are introduced into the top of the condenser, they are cooled. As the gas cools, it condenses and is discharged from the bottom of the condenser as a high-pressure liquid.

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evaporator

The evaporator is located in the car and used as a heat absorption component. Evaporators provide multiple functions. Its main duty is to remove heat from the car. The second advantage is dehumidification. When the hot air flows through the aluminum fins of the cooler evaporator coil, the moisture in the air condenses on its surface. The passing dust and pollen stick to the wet surface and then are discharged outside. On wet days, you may see water dripping from the bottom of your car. Please rest assured that this is completely normal.

The ideal temperature of the evaporator is 320 degrees Fahrenheit or 00 degrees Celsius. The refrigerant enters the bottom of the evaporator as a low-pressure liquid. The hot air passing through the evaporator fins makes the refrigerant boil (the boiling point of the refrigerant is very low). When the refrigerant begins to boil, it will absorb a lot of heat. This heat is then taken out of the car by the refrigerant. Several other components work with the evaporator. As mentioned above, the ideal temperature of the evaporator coil is 320 F. Temperature and pressure regulating devices must be used to control its temperature. Although there are many kinds of equipment used, their main functions are the same; Keep the low pressure in the evaporator and prevent the evaporator from freezing; A frozen evaporator coil will not absorb as much heat.

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pressure-regulating device

Controlling the evaporator temperature can be achieved by controlling the refrigerant pressure and the flow rate into the evaporator. Since 1940, many different pressure regulators have been introduced. The following are the most common.

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Orifice tube

Bore pipes, perhaps the most commonly used, can be found in most GM and Ford models. It is located in the inlet pipe or liquid pipeline of the evaporator, somewhere between the condenser outlet and the evaporator inlet. In a normal operating system, this can be found by determining the area between the condenser outlet and the evaporator inlet that suddenly changes from hot to cold. Then you will see small dents placed on the pipeline to prevent the nozzle from moving. Most orifice pipes used today are about 3 inches long and consist of a small copper tube wrapped in plastic with a filter screen at each end. It is not uncommon for these pipes to be blocked by small debris. Although it is not expensive, it is usually between three and five dollars, but replacing one requires recovering refrigerant, opening the system, replacing the throttle pipe, emptying it and then filling it. In view of this, it may be meaningful to install a larger pre-filter in front of the orifice pipe to minimize the risk of recurrence of this problem. Some Ford models have a permanently fixed orifice tube in the liquid pipeline. These can be cut off and replaced with a combined filter/orifice plate assembly.

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heating power expansion valve

Another common refrigerant regulator is the thermal expansion valve (TXV). Usually used in import and after-sales systems. This type of valve can sense temperature and pressure, and is very effective in regulating the refrigerant flow to the evaporator. There are several common variants of this valve. Another example of thermal expansion valve is Chrysler's "H type". This type of valve is usually located on the firewall, between the inlet and outlet pipes of the evaporator and the liquid and suction pipes. Although these types of valves are effective, they have some disadvantages compared with orifice piping system. Like orifice pipes, these valves may be blocked by debris, but there are also small moving parts that may get stuck and fail due to corrosion.

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Liquid storage dryer

The receiver dryer is used on the high pressure side of the system using the thermal expansion valve. This metering valve requires liquid refrigerant. To ensure that the valve gets liquid refrigerant, a receiver is used. The main function of liquid storage dryer is to separate gas and liquid. The second purpose is to remove moisture and filter dust. There is usually an observation window at the top of the liquid storage dryer. This observation window is usually used to charge the system. Under normal operating conditions, there should be no bubbles in the observation window. It is not recommended to use the observation window to inflate the R- 134a system, because the turbidity and oil separated from the refrigerant will be mistaken for bubbles. This error can lead to a dangerous overcharge situation. There are various receiving dryers and several different desiccant materials are used. Some desiccant is incompatible with R- 134a. The type of desiccant is usually indicated on the label attached to the liquid storage dryer. The new receiver dryer uses XH-7 desiccant, which is compatible with R- 12 and R- 134a refrigerants.

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storage battery

The accumulator is used in the system with throttling pipe to measure the refrigerant entering the evaporator. It is directly connected to the evaporator outlet to store excess liquid refrigerant. Introducing liquid refrigerant into compression may cause serious damage. A compressor is designed to compress gas instead of liquid. The main function of the accumulator is to isolate the compressor from any harmful liquid refrigerant. Accumulators, like liquid storage dryers, can also remove debris and moisture from the system. It is best to replace the accumulator every time the system is turned on for overhaul, and when moisture and/or debris are worrying. Moisture is the number one enemy of air conditioning system. The moisture in the system is mixed with refrigerant to form corrosive acid. If in doubt, it may be beneficial for you to replace the accumulator or receiver in the system. Although this may make your wallet uncomfortable temporarily, it will have long-term benefits for your air conditioning system.

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