How it works: all the subtleties of car air conditioners
In recent years, with the advent of summer, abnormal heat often comes to our latitudes. Temperatures of +40C and high humidity have become commonplace. All this leads to the need to use air conditioning. If he is. Well, in case of absence, motorists are increasingly thinking about installing it.
In the past, air conditioning was considered a luxury item. Today it can be found even in budget cars. However, there are a significant number of vehicles (mostly second-hand) that do not and did not have air conditioning.
In this article, AutoPortal will talk about the principles of operation, design, operation of car climate systems, as well as how to check the air conditioner before buying a used car.
Comfortable microclimate conditions and the principle of operation of the air conditioner
Comfortable conditions mean the optimal temperature and humidity for the human body, which can vary depending on the external temperature and even the duration of the trip. And the flow of air directed to one or another part of the body plays a role.
As can be seen from the table, there is a significant difference in driver comfort in a car with and without air conditioning. In addition to comfort, safety is also an important factor, since under adverse conditions the driver's concentration and responsiveness are significantly reduced.
The comfortable temperature in the passenger compartment of the car is determined by the temperature of the outside air and the amount of air exchange. Here are the values for comfort given by the Volkswagen service manual/:
At low outside temperatures, e.g. -20ºC
High interior temperature 28 ºC, large air exchange 8 kg/min
At high temperatures, e.g. 40 ºC
Moderate interior temperature 23 ºC, high air exchange 10 kg/min
At moderate temperatures, e.g. 10 ºC
Moderate interior temperature 21.5ºC, low air exchange 4 kg/min.
Comfortable conditions mean the optimum temperature and humidity for the human body
It is clear that the conventional ventilation / heating system, to which VAZ owners are accustomed and whose capabilities are limited to blowing the cabin and supplying heat, is virtually powerless in the summer. Only an air conditioner can cool the air supplied to the passenger compartment and remove excess moisture.
The principle of operation of the air conditioner
The scheme of operation of the air conditioner is simple and does not fundamentally differ from the operation of a household refrigerator. The air conditioner is a sealed system in which freon circulates. The principle of operation is based on the law of physics, which states that when a substance changes from a liquid state to a gaseous state, heat is absorbed, and when a substance changes from a gaseous state to a liquid, heat is given off. The substance that circulates in the air conditioning system, in our case, is freon, called the refrigerant. Its task is to absorb heat in the car interior, thus maintaining a comfortable temperature. Freon absorbs heat in the gaseous state and releases it in the liquid state. This is how heat from the car interior is transferred outside.
Compressors There are several types of air conditioners. They differ in drive and type. The most widely used compressors are piston or rotary type, driven by the crankshaft of a car, as the simplest and most efficient. The advantage of self-driven compressors is that they can run when the vehicle engine is off. For machines with start-stop systems, Sanden has developed compressors that run on the engine or on their own drive, depending on the mode.
Each car model has its own air conditioning system layout.
Air conditioners also differ in the scheme of operation. They are divided into two types. The first involves regulating the flow of refrigerant using dryer receiver And expansion valve(TRV), the second - through battery And throttle. The first type includes air conditioners of Japanese, French, Italian and Korean cars. To the second - most American cars, as well as models of Audi, Volkswagen, etc.
Capacitor, - an aluminum or copper heat exchanger in which the refrigerant condenses.
Evaporator, - a source of coolness in the car. It is a heat exchanger, in aluminum or copper version, in which the refrigerant passes from the liquid phase to the gaseous one.
Fans. The task of the condenser fan is to remove excess heat from it. The task of the evaporator fan is to supply cool air to the interior of the vehicle.
Automotive air conditioner control and protection system
Volkswagen/Audi manual air conditioning control and protection system:
1 Air conditioner switch
2 Safety valve on the compressor
3 Condenser fan
4 Pressure switch
5 Coolant temperature sensor
6 Condenser fan thermal switch
7 Evaporator temperature sensor
8 Evaporator fan
9 Engine control unit
10 Electromagnetic clutch
TO Air conditioner control unit (and/or control unit for condenser fan, depending on air conditioner version).
The air conditioning control system is a set of sensors and actuators
The air conditioning control system is a set of sensors and actuators, in particular:
Control block. It processes signals from sensors and controls actuators, ensuring a constant pressure in the refrigerant circuit and a given cooling capacity.
Electromagnetic clutch. When the air conditioning system is turned on, the compressor starts.
Pressure switch. In case of emergency low or high pressure, the pressure switch sends a signal to turn off the compressor. In case of overpressure, a command to turn on is given condenser fan one step up.
With a critical increase in pressure safety valve vents the refrigerant until normal pressure in the system is restored.
Condenser Fan Thermal Switch. Turns on the fan when the refrigerant temperature is high.
Evaporator temperature sensor. Shuts off the compressor when there is a risk of icing.
coolant temperature sensor. Turns off the compressor at high freon temperature.
The temperature of the cooled air is usually much lower than necessary, so part of it is directed through a damper through the heater's heat exchanger, where it is heated. In manual systems, the driver himself determines the temperature in the cabin, sets the speed of the fresh air blower and adjusts the degree of opening of the temperature damper.
Most modern cars have automatic air conditioning control. There are several climate systems that differ in their functionality. The temperature set by the driver in the cabin is maintained and adjusted automatically, taking into account the data received from various sensors that inform about solar radiation, outside air temperature, etc.
The outside air temperature sensor measures the outside temperature.
The temperature sensor in the air duct monitors the temperature of the air leaving the evaporator.
The solar radiation sensor controls the speed of the fan in the cabin.
The microclimate in the cabin can be divided into several zones (often 1, 2 or 4 - in luxury cars), each can have its own parameters.
All information received from the sensors is processed in the control unit, which controls the actuators. The set temperature in the climatic zones is maintained by means of actuators that control the corresponding dampers.
The microclimate in the cabin can be divided into several zones
The temperature range in which the climate system operates in automatic mode is usually from 18ºС to 28ºС. If the air conditioner is in the "Auto" mode, it turns on along with the ignition, displaying the readings of the sensors and the value of the set temperature on the control panel. It is possible to set a temperature outside this range, in which case the unit will operate at maximum cooling or heating capacity. When the outdoor air temperature is less than 5ºС, the system automatically turns off.
Estimated cost of some original car air conditioners:
1.3, 1.5, 1.6 - 13.000-15.000 UAH.
N100, N150 - 9.000 UAH
B5 1.6 - 17.000 UAH
Installation of the air conditioning system
Installation, if you do not have sufficient experience, it is better to entrust a service station with a good reputation.
Briefly describe the installation procedure can be described as follows:
Compressor installed in the engine compartment, close to the engine crankshaft pulley. During installation, it may be necessary to dismantle the air filter, generator, etc. The position of the compressor pulley is chosen so that the drive belt is tensioned with the required tension and without distortion.
Capacitor is installed in front of the regular heating radiator, an additional fan can be installed together with the condenser.
Evaporator most often installed under the dashboard.
Pipelines. For their laying, it may be necessary to drill additional holes in the engine compartment. Lines must be securely fastened and connected. Do not fasten the lines with clamps, there are special fasteners for this.
Then the wiring is connected, the electronic engine control unit is programmed, evacuation and refilling with freon is carried out.
The estimated cost of installation can vary widely. For example, the cost of installing an air conditioner on a Daewoo Nexia is 3.500 UAH. on the official service, and on the unofficial service station it can be installed for 1.600-2.500 UAH.
Air conditioner care
To ensure that the efficiency of the air conditioner does not deteriorate, it is necessary to regularly clean the condenser radiator. Clean once a quarter - after winter, after the season of "poplar fluff", etc. Change your cabin filter promptly.
Watch for freon lines, places of their connections. If oil smudges, traces of condensate are visible, you may have a freon leak, the refrigerant line is clogged. If you have a system with an expansion valve, the receiver should have a viewing window through which you can assess the state of the freon. If a lot of bubbles are visible (as in soda) or turbidity is visible, the system is depressurized.
Mold can form on the evaporator, and moisture can stagnate in the drainage system. In order not to keep such a hotbed of bacteria in the car, 10-15 minutes before parking, you need to turn off the air conditioner and ventilate the car interior by turning on the stove fan. It is also necessary to monitor drainage.
Check compressor belt tension.
If you do not use the air conditioner, it must be turned on periodically (once a month) for 15-20 minutes so that the oil does not stagnate in the system and the seals do not dry out.
Service maintenance of air conditioners
Freon should only be charged if it leaks. Refueling involves diagnosing the system. Service on a new air conditioner is carried out every 2-3 years.
To find a quality service, you need to do a little research.
To find a quality service, you will need to conduct a small investigation, since, according to motorists and servicemen, even the "brand" service station is not a guarantee of quality service. Ask if the service station does evacuation, what they evacuate, with a vacuum pump or freon purge (which is useless).
Fill the air conditioner only with freon, the brand of which is indicated by the factory.
Don't buy into the cheap cost of refueling, it's not worth the risk. There is fake freon on sale, which contains impurities of chlorides, other freons, which contribute to corrosion and are sometimes dangerous to health.
Refueling oil, which is added during refueling, must be compatible with the brand of freon!
The range of prices for after-sales service in Kiev:
Diagnostics of the air conditioning system - 50-255 UAH.
Full filling with freon from 400 UAH.
Full diagnostics and refueling with freon from 300 UAH.
Disinfection - 100-300 UAH.
Diagnostics of the air conditioner compressor - from 50 UAH.
Air Conditioning Tips
The safe temperature difference between the interior and the street is 5-10ºС.
Turn on the air conditioner if you plan to spend more than 15 minutes on the road.
The surest sign of a possible breakdown is a deterioration in the efficiency of the air conditioner. Moreover, when driving, the air conditioner can work normally, but it is clearly not enough in a traffic jam.
A change in the sound of the compressor, most likely, indicates a malfunction in the system.
Checking the air conditioning system when buying a used car
When buying a used car, the best option would be to have a specialist with the necessary equipment diagnose it. If you do not have such an opportunity, use some tips that will not give you a 100% guarantee, but will increase the chances of buying a car with a working air conditioner.
The air conditioning system must work. If it is not working at the moment (like "freon was lowered for the winter"), consider that it does not work at all, this will reduce the cost of a car by several thousand hryvnias. The ideal sign of system performance is, of course, the temperature in the cabin.
Knowing what the system components look like and their approximate location, you need to make sure they are present and evaluate the appearance.
If the receiver is equipped with a viewing window, evaluate the condition of the freon (more on this above).
If the air conditioner is not working at the moment (such as "freon was lowered for the winter"), consider that it does not work at all
If you can't spend enough time diagnosing and waiting for the cabin to cool down, check the temperature at the "control" points. After turning on the air conditioner, tightly wrap your hand around the metal part of the tube (the thickest tube) of the evaporator that leads to the compressor. When the compressor is running, the metal becomes very cold. The metal part of the tube (which leads from the compressor to the condenser) becomes warm or hot when the compressor is running, depending on the outside temperature. The thinnest tube that leads from the evaporator to the passenger compartment should also be warm or hot when the system is running, if you cannot hold your hand on it - there may be a problem with the evaporator blower fan, a dirty evaporator or recharging the system with freon.
Check the temperature of the air in the deflector with a thermometer (not mercury!) By directing the air flow there at the maximum speed of the system and at the minimum cooling temperature. With a normally working air conditioning system, the temperature should drop to 5-10ºС.
Inspect the freon lines, their connections and connections. In the event of a leak, as described above, traces of oil and condensate will be visible.
To check the car in winter, you need to drive it into a heated garage for several hours. In the absence of such an opportunity, it is worth trying to warm up the interior to the "hot" state, on simple systems without an outside air sensor, the air conditioner should start. In systems with climate control, you can try to turn on the recirculation button - on many machines, in this case, the control unit no longer focuses on the outside temperature.
Instead of an epilogue
Many drivers are stopped from installing air conditioning by increased fuel consumption and worse acceleration dynamics when it is turned on. Yes, it is, but health is more expensive (besides, fuel consumption also increases with open windows). The main thing is to use "cooling" wisely and from time to time to diagnose the system.
