03/04/2022 8,032 Heating and air conditioning system
Author: Ivan Baranov
Drivers have long been accustomed to the comfortable conditions in the cabin provided by air conditioning. Therefore, its breakdown significantly affects the well-being of the driver and passengers. Repair and maintenance of car air conditioners is usually carried out by specialists at a service station, but in order to save money, the driver can do this with his own hands, having the necessary tools at hand. The article describes how to detect malfunctions in a car's air conditioner and repair it yourself.
The air conditioner consists of several elements that form a closed system with a front and rear circuit through which freon - coolant - moves. Circulation through the rear and front refrigerant circuits is carried out by a compressor. The compressor compresses the freon, providing pressure in the system. In the compressor, the refrigerant is heated and comes out as a gas. Freon enters the condenser, where the system cools the gas and it turns into condensate.
Then the refrigerant is cleared of impurities in the receiver-dryer and moves to the thermostatic valve (TEV). Next, the liquid refrigerant enters the radiator, where it again turns into a gaseous state. At the same time, it cools the air by absorbing heat from it. The radiator greatly cools the air as it passes through it. Cooled air enters the cabin. Freon returns to the compressor through the rear circuit, and the cycle repeats from the beginning.
Diagram of the car ventilation and air conditioning system
Any element of the air conditioning system may become unusable, which will affect the operation of the entire system. Therefore, you need to figure out what malfunctions may arise, how to diagnose them, why this or that malfunction occurred, and how to fix it.
[Hide]
Air conditioner won't turn on
This usually happens for two reasons:
- The first is that there is a leak and there is no refrigerant in the system or its quantity is insufficient. To check, you need to connect pressure gauges. And if the pressure in the system is less than 2 atm. The emergency pressure sensor turns off the power to the compressor. The compressor shaft does not rotate from the drive belt and pressure is not created in the system. The pressure sensor thereby protects the compressor from running without refrigerant. An even easier way to make sure that there is not enough refrigerant in the system is to bridge the sensor contacts. In this case, two faults are checked at once: there is no refrigerant, or there is an open circuit in the compressor power supply circuit.
When the engine is not running, with the ignition and air conditioning on, the sensor contacts are bridged and the electric clutch is activated; a characteristic click should be heard. If this does not happen, then there is no refrigerant. This can be seen when connecting pressure gauges. The pressure in the system must be more than 3 atm.
- The refrigerant is fine, then you need to look for the problem in the electrical circuit. This could be a break in the electrical wiring, or the sensor itself has failed, or the temperature controller has failed, or the fuse may have blown. There are many possible problems here. These can be eliminated by checking the presence of power at each stage of the electrical circuit. If the air conditioner turns on and operates but there is no required cooling temperature, a malfunction occurs in the air conditioning system.
Fixing freon leaks
If the car air conditioner turns on, but it does not cool the air in the cabin, then you need to find the reason why. The reason for this is most likely a freon leak on the front or rear circuit, at the joints. This is the most common air conditioner malfunction. This breakdown can be avoided if you perform timely diagnostics and maintenance of the machine.
Before repairing a refrigerant leak, you need to locate the leak locations. Diagnostics are performed without tools using special gas analyzers that detect the presence of freon and can pinpoint the location of the leak.
The second method is to charge the system with refrigerant containing ultraviolet dye. Checking the front and rear circuits, as well as the entire system, is carried out using an ultraviolet lamp. If a leak is detected, you must either replace the part, or, if the part is metal, install a patch, having prepared the necessary tools and materials. Worn rubber parts should be replaced with new consumables.
Freon leak detection
Insufficient cooling temperature
Compressor malfunction resulting in insufficient cooling temperature has many causes. When the compressor is turned on at full power, the air temperature leaving the evaporator should be 6 degrees Celsius.
The first reason is that there is not enough refrigerant in the system.
This may be indicated by low pressure in the high pressure line. It is difficult to determine exactly how much refrigerant needs to be refilled. It’s good if there is a viewing window located on the receiver. Sometimes it is built separately into the high pressure line. If, when you turn on the compressor, you can see a lot of bubbles in it, as if they are foaming, then there is not enough refrigerant and refilling is necessary. It is better to completely remove the refrigerant from the system. And recharge the air conditioner. Or refill in small portions of 100g while checking the operating parameters of the air conditioner.
The next reason for insufficient cooling temperature
consists in weak airflow to the condenser radiator. It becomes clogged with dust and dirt from the outside, causing insufficient cooling of the radiator. The refrigerant is supplied to the radiator under high pressure in a gaseous state. There it cools and turns into a liquid state. If cooling is insufficient, the refrigerant in the form of gas will enter the evaporator and evaporation as such does not occur, but during evaporation the cooling process of the evaporator radiator occurs. If the evaporator honeycombs from the outside are clogged, cooled air simply does not enter the cabin. In sufficient quantity. Radiators must be clean and allow good air flow.
Recommendations for preventing car air conditioner malfunctions
The air conditioning system is a rather capricious device. If you are purchasing a new car, then maintaining the air conditioner for a certain period of time will not require excessive effort from you. It's another matter if the purchase is made on the secondary market. It is imperative to check the operation of the climate system! If the seller starts feeding you standard phrases like “there is no freon in the system, they let it go for the winter” or “the belt broke, I keep forgetting to buy a new one” - most likely, the air conditioning system is simply faulty. This is reason enough to reduce the cost by about $500, which is the average cost of air conditioner repair.
Many modern cars are equipped with turbocharged power units, which require a large amount of oncoming air. To do this, they are equipped with air intakes and decorative grilles with large cells. In such cases, you can extend the life of the air conditioner by installing a metal or nylon fine mesh on the radiator. It will protect it from dirt, reduce the number of washes and prevent insects and small stones from getting on the radiator - the remains of midges can be very difficult to get rid of, and there is no need to talk about the danger of encountering stones at high speed.
If you turn on the climate system in winter, try to strictly adhere to the simple recommendation - start the air conditioner only after the interior has warmed up sufficiently. In particular, the dashboard should not be very cold to the touch. Otherwise, the correct operation of the air conditioning system sensors at the initial stage of its operation is not guaranteed. After a trip, the air conditioning should be turned off a few minutes before turning off the engine, leaving the heater on. In this case, the hot air will have time to dry the air ducts, reducing the likelihood of the formation of favorable conditions for the proliferation of bacteria and microbes.
Air conditioning compressor faulty
If the compressor fails, there will also be no normal cooling. The compressor is an expensive structural element. The decision to cull it should be quite responsible
The malfunction of the air conditioning compressor and how to eliminate it can be judged by the pressure that appears in the high and low suction pressure lines. In this case, there is increased pressure in the low pressure line and decreased pressure in the high pressure line. A faulty compressor has a hard time creating discharge pressure and therefore takes insufficient refrigerant from the low pressure line. If these pressure readings are present, it can be said that the compressor has failed.
cabin filter
On some car models, the cabin ventilation system is designed in such a way that the cabin filter maintains a decent flow capacity for a long time, while on others it is inevitable to replace the element once a year.
On some car models, the cabin ventilation system is designed in such a way that the cabin filter maintains a decent flow capacity for a long time, while on others it is inevitable to replace the element once a year.
The compressor switches on and off frequently.
For this reason, the system does not reach operating pressure and the air conditioner does not operate efficiently. Usually it's related.
- with excess refrigerant in the system.
- In some place the passage of refrigerant is difficult. But as a result of congestion, the required pressure is not created in the evaporator radiator. As a result, the cooling temperature is low.
- The external evaporator radiator may be clogged. Due to poor heat transfer, excess pressure is created in the evaporator. it is difficult to pass the chemical agent.
Fan failure
If the air conditioner fan does not turn on, this is another reason why the compressor and the air conditioner itself may not start. The function of the fan is to further cool the refrigerant. However, not all air conditioners have this element, and breakdowns are quite rare. Symptoms are noise during operation or a complete absence of any rotation. The temperature inside the car will be slightly higher than necessary.
Causes include worn bearings, electrical problems, mechanical defects and damage.
Belt slipping on compressor pulley
When the required pressure is built up, the belt slips and the pressure in the system drops. That is, the pump cannot create the required pressure. And the processes occurring in the air conditioner are disrupted. The required refrigerant gas temperature is not reached. Accordingly, the evaporation of the refrigerant occurs less intensely. Less energy is spent on evaporation. And as a result, the required cooling temperature is not achieved. The pressure gauge shows that the discharge pressure is below the permissible level.
Low cooling capacity can also be affected by other malfunctions that occur during operation of the air conditioner.
The first reason for the breakdown
The first thing you should pay attention to is noise. Usually, when the early stage of wear begins, the bearing located on the shaft pulley begins to make noise.
This noise can be heard when the air conditioner is turned off and the shaft is idling. This is expressed in a monotonous, unpleasant hum.
There can be two reasons for this buzzing:
- The shaft drive belt is tightened.
- Critical wear of the bearing as a result of natural wear.
Low suction pressure
If we observe low suction pressure, we can check the following faults:
- insufficient amount of refrigerant in the system. The air conditioner needs to be recharged.
-moisture has accumulated in the system. Urgent refilling required.
-The thermostatic valve or nozzle is clogged; they are located at the inlet of the evaporator and spray liquid refrigerant for its subsequent evaporation. This is the thinnest place in the system and is the first to become clogged. The elements that clog bottlenecks in the air conditioning system can be pieces of rubber from a decomposing hose or silica gel found in the receiver dryer. In the case of the expansion valve, it becomes clogged, so only its replacement is possible. Also, particles from a damaged and previously replaced compressor can serve as a source of clogging. In general, if the compressor is destroyed, it is recommended to completely replace the air conditioner on the car. Otherwise, the problem with clogging of the compressor elements will occur constantly. It happens that pieces of rubber clog some kind of decomposed hose. The search for such faults is carried out by disassembling the system and blowing its elements with compressed air.
If such a malfunction is not detected in a timely manner, the compressor may fail. Since it encounters resistance, it begins to heat up and fails.
If the expansion valve or hoses become clogged, the discharge pressure becomes higher than normal, and the suction pressure becomes less than 0. In this case, it is necessary to immediately stop operating the compressor. And look for the cause of the air conditioner malfunction and ways to eliminate it.
Performance assessment
In the air conditioning system, the components most susceptible to wear are the compressor and heat exchanger. When the question arises - why the air conditioner in the car does not turn on, you should make sure there is no contamination and assess the level of the working fluid. You can also carry out quick diagnostics by assessing the performance of the device.
How to do a quick assessment:
- Having started the engine, turn on the air conditioner;
- when you touch the thick tube, you should feel an increasing coldness;
- when turned off and then turned on, a cold wave should appear;
- at the same time, the thin tube becomes hot, its temperature should increase along with the ambient temperature.
When heat and cold are not clearly expressed, diagnostics and inspection at a service center are required.
High suction pressure
Occurs when:
- faulty compressor, as already described above
- excess refrigerant. The compressor does not have time to pick up refrigerant for injection
- faulty TRV. In this case, it is open and does not close. The refrigerant circulates through the system without resistance, thereby reducing the discharge pressure. This symptom is very similar to a compressor malfunction. And if in doubt, it is necessary to start troubleshooting with the expansion valve. As a rule, it is possible to determine accurately only after replacing it. If the expansion valve is jammed, then cleaning and repair will lead to nothing.
Washing methods
Car air conditioning can be cleaned chemically or mechanically. The chemical method involves the use of foam and aerosols. The second method is resorted to if the first one turns out to be useless.
Special cleaning products cost from 150 rubles to 1000 rubles. Cheap cleaners often do not give the desired effect. That is why drivers try to build something from scrap materials. For example, unpleasant odors are removed using chloramine B, lysoformin 3000 and chlorhexidine. The solution is sprayed over contaminated areas. Don't forget to ventilate the salon after treatment.
