Why the air conditioner in the car does not turn on: possible reasons and expert advice

According to inexorable statistics, we spend one sixth of our lives driving. And each of us wants to spend this time in comfort: at least with air conditioning. Now this invention seems something trivial, but in the first half of the last century, climate control systems occupied half the trunk, and their cost was a third of the price of the entire car.

Do you need to know the structure of a car air conditioner? Definitely yes. Understanding the principle of its operation, it is easier to find the cause of the problem.

How the air conditioner works, what problems can be expected from it and how to service it was told by Dmitry Ivanov, service manager of the Maintenance Department of the Avtopraga company, the official dealer of ŠKODA.

Why is this happening?

If the air conditioner suddenly stops working or turning on, you should not immediately go to the nearest service station and pay for diagnostics and repairs. You can check the unit yourself - many faults can be fixed with your own hands. If the air conditioner does not turn on, experts recommend checking the main units. And to understand what to check first, you need to know some causes and symptoms.

In fact, there are only three reasons why this device may not turn on. This is a non-functional start button, poor or absent contact on the compressor, as well as a low amount of refrigerant. These are all things to check if your air conditioner won't turn on.

Weak air flow

Usually it is enough to replace or at least clean the cabin filter. If it is missing, the radiator comb may become clogged with fluff and other dirt - in this case, serious disassembly is often necessary.

In modern vehicles with electronically controlled air dampers, faulty or unadapted servos can cause insufficient air flow. Adaptation of the climate system is carried out using a diagnostic scanner. If a malfunction is identified, its elimination may require deep disassembly of the entire climate system.

A malfunction of the fan or fan speed controller can also cause insufficient air flow, but such a malfunction is usually detected by ear: when changing the mode, the sound of the operating fan does not change at all.

Checking the button and wires

Every car has some kind of “childhood” diseases and weak points in the electrical system. Over time, these places can cause serious problems for the owner. On many cars, you can observe low quality soldering in the control unit of air conditioning or climate control systems. You can often read on specialized forums that wires have fallen off the compressor.

Speaking about the power button, it should be noted that when you press it, the ECU receives a request to turn on the air conditioning. If there are any problems in the button or its circuit, the control unit simply does not know about the desire of the car owner to create a comfortable temperature in the cabin.

In this case, you can only check the connectors on the compressor and the button using a multimeter. If the circuit is working and the ECU receives a request, the unit does not have to complete the task. Therefore, if everything is in order, but the air conditioner does not turn on, you need to dig deeper.

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Refrigerant deficiency

If there is not enough freon in the system, then the control unit will never turn on the air conditioner, or rather, it will not start the compressor. You can spend a long time checking it for serviceability, but it won’t do any good. There is little you can do here with your own hands - experts recommend contacting professionals for repair, diagnostics and refueling of this equipment. Many car enthusiasts think that they can charge the air conditioner with their own hands - this is a misconception. It will not be possible to do everything using technology in a garage.

What to do if the air conditioner in the car does not cool? The reasons are known, it remains to eliminate them

As you can see, you can easily eliminate only the first cause yourself - dirt between the radiator fins. However, on many car models even this is not easy to do. Sometimes it is possible to get to the space between the radiators only after dismantling the condenser. And it is better to entrust this to specialists.

To eliminate other faults, you need special equipment - pressure gauges, a leak detector (a device for determining the location of a freon leak). If there are cracks in the aluminum tubes, you will have to use argon welding.

Unfortunately, in the hottest summer months, air conditioners at service stations simply do not have time to serve all customers. Therefore, it is better to think about this in advance. We advise you to check the operation of the car’s climate system in the spring, undergo diagnostics and preventive maintenance at a service center. In this case, you will be sure that the air conditioner will not fail at the wrong moment and will not leave you alone with the heat.

About self-refueling of car air conditioners

Some motorists talk about cans of R134 freon, as well as how to refuel using this product. You should not use these tips. Nothing good will come of this, and the worst thing is water hammer.

There are only two types of filling - liquid phase or gaseous. If the cylinder is in the upper part, then refilling is carried out in the gas phase. If the can is upside down, the freon will be liquid.

The phase in the form of gas can be pumped into any pipeline - both low and high pressure while the compressor is running. But liquid freon can only safely flow into high-pressure lines. If you remember how an air conditioner works, the compressor compresses gas, but not liquid. If you put liquid in front of the compressor, it will break.

It is also necessary to remember that in an air conditioner it is not the freon pressure that is important, but the weight. The plate located under the hood shows the volume of refrigerant and oil in grams, but in pressure units.

For refueling, it is better to use the services of professionals who, using a special installation, will perform the procedure correctly and without harm to the system. The cost of the service is about 700-1000 rubles.

How it works

A mobile climate control device is not much different from a regular refrigerator in our kitchen. This is a sealed system with a closed circuit through which refrigerant gas circulates.

When the system starts, the compressor compresses the refrigerant, causing it to become very hot.
Hot gas under high pressure is driven into a condenser, which is popularly called an “air conditioner radiator,” where it cools and turns into liquid.
Once in the receiver-dryer, the liquid refrigerant is filtered from dust and other impurities. The freon then enters a thermostatic expansion valve (TEV), which returns it to a gaseous state. The expansion valve is the transition point from high pressure to low pressure in the system.
The next destination is the evaporator, somewhat similar in structure to a small radiator. The temperature of the gas entering it tends to zero, and interacting with the warm air in the cabin, it begins to boil, cooling the radiator to an icy state.
The fan “blows the cold away” from the evaporator into the cabin. Completing the cycle, the refrigerant again enters the compressor.

Passing through the evaporator channels, the air leaves moisture on its surface. It falls into the pan and is removed through a special condensate drain.

If the compressor fails

It happens that the button works, the amount of refrigerant is sufficient, but the device does not want to work. The air conditioning compressor most likely does not turn on here. It may not work due to a loose or broken drive belt. Also, the compressor will not turn on if there are refrigerant leaks. But the causes of leakage can be various defects on the device body, a broken line, or a worn rubber gasket. These are the main reasons when it is impossible to start the air conditioning compressor.

First of all, check the condition of the belt. It is important that it is taut. If cracks appear on the belt, this indicates a faulty element. This drive needs to be replaced. If everything is in order with the belt, but there are minor damages, it should be replaced.

Next, it is recommended to carefully inspect the unit body. There should not be any drips on it. There could be an oil or refrigerant leak. If drips are visible, this is a reason for a serious inspection. For more accurate diagnostics, the unit is removed from the car. Defects in the housing through which the refrigerant escapes cannot be repaired. The device should be replaced with a working one. Experts say that modern car air conditioners are difficult to repair, and most components are completely disposable.

It is also recommended to diagnose the gasket. There should also be no freon residues on it.

Next, each tube that is part of the system is checked. They are rubber, which means they can crack or fray. As a result, the refrigerant leaves and the air conditioner does not want to work.

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Other faults

There are several other reasons that do not always, but still lead to the failure of air conditioning compressors. Let's take a look at them, even though they are quite rare.

The first reason is problems in the electrical part. The practice of repairing and servicing car air conditioners shows that most often the pressure sensor fails. Its task is to turn off the system when its pressure level is critical. If the sensor fails, this can lead to various consequences. Most often the line breaks. This is accompanied by steam from under the hood and the dashboard in the cabin. However, the sensor fails quietly, without any effects. It simply “hangs” in a position where the pressure is high and the air conditioning in the car does not turn on.

A rather rare, but still existing problem is a dirty capacitor. If it is clogged, the pressure inside the system increases. The sensor signals that the compressor is turned off. Such a problem will not be visible immediately, but only after several minutes of operation of the air conditioning system. Only in the most difficult and advanced cases will the air conditioner not turn on. This problem can be solved. In this case, the system is washed and the condenser is removed for cleaning.

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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.

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Price issue

The cost of services for refueling or refilling an air conditioner in large cities of Belarus starts from 10-15 rubles. (but the final cost depends on the volume of materials used), they charge the same amount for checking the system for leaks. But disinfection, which is especially relevant during the spread of coronavirus, is estimated at about 20-35 rubles.

The cost of a new compressor, as a rule, exceeds 600-700 rubles, so in the case of used cars, a used part is used, the price of which for older models may even be lower than 80-90 rubles, but for relatively fresh and premium ones it may well exceed 250-300 rubles. It’s the same story with a radiator (condenser): a new one will cost hundreds of rubles, a used one, as a rule, can be found for 50-150 rubles, however, it all depends on the car model. The evaporator is several times cheaper; the same used version usually costs 30-80 rubles. A receiver-dryer is estimated at 180-250 rubles, but if a replaceable cartridge is provided, it will cost several times less.

The service for refilling the air conditioning system includes checking the system for leaks. Our network has a wide selection of cabin filters. 15 years of experience in car servicing. More details