Why does my car air conditioner blow hot air?
Content
The car air conditioner rarely fails suddenly, but it usually happens before the start of the summer season. Sometimes due to the lack of proper prevention, but breakdowns also occur. Diagnostics will be required, since there can be many reasons.
When does hot air flow from the air conditioner to the car?
As part of the air cooling system, there are a lot of potentially unreliable components and parts:
- compressor with electromagnetic clutch and idling bearing;
- condenser (radiator) in a block with the main engine cooling radiator and fans;
- filter-drier at the radiator;
- high and low pressure lines, usually made of thin-walled aluminum tubes with O-rings;
- refrigerant (freon), which includes oil for lubricating the system from the inside;
- valve-regulator;
- evaporator in the form of a saloon radiator;
- control system with sensors and switches;
- a complex of air ducts and dampers with control actuators.
Typically, the evaporator is located in the same air conditioning unit with the heater radiator, valves are rarely installed in the liquid flow, so it is not surprising that in case of failures, cold air can change to hot. But in summer, any air will be cooled when everything is in order or warm when there are malfunctions.
Low refrigerant
When refueling the system, a strictly defined amount of freon and lubricant is pumped into it. It is no longer possible due to the risk of damage, there is also an incompressible liquid phase of the refrigerant in the system, and if there is not enough carrier, then the heat transfer efficiency is sharply reduced.
There can be several reasons for the lack of freon:
- errors when refueling the system;
- the system served for a long time without refueling;
- leaks occurred due to loss of tightness by pipelines or seals.
If the problem arose suddenly, then it is worth looking for a leak, if gradually over time, then it is worth starting with a refueling.
Weak condenser cooling
The radiator of the air conditioner is designed for cooling by natural flow or forced by a fan. As a rule, the fan turns on simultaneously with the air conditioner, because in the heat and in the presence of a hot main radiator nearby, the airflow is not enough in any case.
When the fan fails, or the surface of the condenser honeycomb structure is very dirty, then forced cooling does not help.
Compressor failure
The compressor is subject to natural wear and tear. First of all, the electromagnetic friction clutch that connects the drive pulley to the compressor shaft suffers. The wear of the pumping part is not treated by repair, it is necessary to replace the unit as a whole.
The coupling can be replaced, spare parts are available. Preventive replacement of its bearing is recommended when noticeable noise appears.
With long service life, the pulley also wears out, which manifests itself in the slipping of even a new belt with the correct tension.
Wiring
For proper switching of air conditioner units, it is necessary to have all supply voltages, contacts with ground, serviceability of the control unit, sensors and switches.
Wiring corrodes over time, contacts can disappear in any circuit. The check comes down to the continuity of the wiring, the control of the presence of all power and control voltages. The coupling must be clearly connected when the air conditioner is activated.
Stove dampers and regulators
If the freon compression and evaporation system is working normally, which is determined by the temperature difference between the supply and return lines, then the malfunction should be looked for in the air distribution system of the air conditioning unit.
The climate module in the cabin has a large number of plastic air ducts and controlled dampers. They must be securely sealed and move confidently under the control of mechanical rods, cables and electric servos.
Over time, the drives fail, the rods can collapse and disconnect in the area of the tips, and the dampers themselves deform and lose their seals.
The air distribution begins along abnormal paths, which is immediately noticeable by the temperature change in the zone of the outlet deflectors at different levels in height.
How to find the reason why the air conditioner blows warm air
First of all, it is necessary to divide the search area in the directions of creating a temperature difference between the condenser and the evaporator and the air flow control system.
The first includes the compressor, radiators, valve and pipelines, the second - air ducts and dampers. Electronics serves both components of the system.
Checking the fuses
The power circuits of all equipment related to air conditioning can be protected by one or more fuses.
Information about this and their location can be found in the relay and fuse placement tables available in the vehicle's accompanying documentation.
Fuses can be removed and checked with a multimeter ohmmeter or just an indicator light by connecting it in series to both terminals of the socket with a fuse inserted into it. Inserts that are oxidized or distorted due to overheating must be replaced.
A fuse can fail on its own, but more often it blows from short circuits in the circuit it protects. Visual control of wiring and continuity of suspicious areas will help.
Computer diagnostics
You can read and check air conditioning control errors using a scanner connected to the vehicle's diagnostic connector.
After pointing out a specific fault with the sensors, they are checked individually along with the wiring. Breaks, short circuits or output of signals from the specified range are possible. Having erroneous information, the control unit will refuse to turn on the compressor.
Finding freon leaks
You can look for refrigerant leaks visually, using the presence of a non-drying lubricant in its composition or using an ultraviolet flashlight.
An indicator substance is added to freon, which converts UV radiation into visible light when the highways are illuminated, the leakage zone will be clearly visible. You may have to wash the engine compartment, since with prolonged leaks everything will glow.
Check the condenser
The air conditioner radiator fails either as a result of depressurization and leaks, or clogging with road dirt. If there is pressure in the system, the freon does not leave, the condenser is warmed up evenly, then most likely it is a violation of heat transfer due to clogging of the honeycomb structure.
It is best to remove the radiator, flush thoroughly under slight pressure, and install with new seals, refilling the system. The filter drier is replaced with a new one.
Checking the compressor drive
You can check the operation of the clutch by applying voltage directly to the connector of its windings. It should close, the pulley will enter into reliable engagement with the compressor rotor. This will be noticeable by increased resistance to rotation when the drive belt is removed.
Compressor Diagnostics
If after checking the operation of the clutch there are doubts about the performance of the air conditioner, then its operation is easiest to check during refueling.
The filling station equipment with control pressure gauges is connected to the lines, one of which will indicate the pressure created by the compressor in the pressure line.
Or easier - after the compressor is activated, the tubes at its outlet should quickly begin to warm up, but its performance can be accurately assessed only with extensive experience.
Fan check
The fan should turn on when the air conditioner is activated and run continuously at low speeds. If such a function is not provided, then you can make sure that its electric motor and power circuits are in good condition by removing the connector from the engine temperature sensor.
After that, the control unit will perceive this as exceeding the temperature limit and turn on the fans. Separately, the motor can be checked by supplying power from the battery to its connector with suitable pieces of wire.
Checking the dampers of the climate system
Access to the dampers is difficult, so to check them you will have to disassemble the front of the cabin. The procedure is laborious and dangerous in that it is easy to damage the plastic latches or loosen the seals, after which additional noises and squeaks will appear.
The air duct system itself is sometimes quite complicated and equipped with electric drives, the diagnostics of which will require a control scanner with service programs. This work is best left to professional electricians.
As well as the repair of the control unit, in which the conductors of printed circuit boards often corrode and solder joints crack. The master will be able to solder defects and restore printed tracks.
