Audi A4 AC is not working Inspection at your home or office.

How this system works:

At its most basic level, a vehicle’s air conditioning system works by intentionally manipulating the temperature and pressure of refrigerant and the direct relationship they have. The process begins with creating high-pressure gas by compressing the refrigerant inside your vehicle’s AC system to raise its pressure and temperature. The refrigerant then flows through the condenser, which turns it into a hot high-pressure liquid before going into the receiver. The receiver – sometimes referred to as a dryer – removes moisture and unwanted particles from the refrigerant. After that, it passes into the expansion valve, or orifice tube, which reduces the refrigerant’s pressure and causes the liquid refrigerant to change its physical state into a cold low-pressure gas.

To perform this change of state from liquid to gas, the refrigerant must have “latent heat,” and it must take that latent heat from the surrounding area inside the evaporator. As the latent heat is pulled from the evaporator core to almost below freezing, the blower motor sends the cold air through your vehicle’s vents. Think of a hot summer day, and you just got out of the pool: The liquid water on your skin starts to evaporate and turn into water vapor. The cooling of your skin is the result of the water pulling the latent heat away from your body to change its state into a vapor.

The air conditioning system is chiefly comprised of the following components:

• Compressor: This is the core of your AC system. Powered by your vehicle’s serpentine belt, the compressor pressurizes the refrigerant. It is turned on and off by way of the compressor clutch.

• Compressor clutch: Before the compressor turns on, a special electro-magnetic clutch called the compressor clutch is necessary to engage and disengage the compressor cycle. The compressor clutch tells the compressor when to turn on and off so the refrigerant is correctly pressurized for use by the condenser.

• Condenser: Located in the front of the radiator, the condenser takes the hot refrigerant and cools it down while also reducing the pressure. This turns the refrigerant into a liquid that can pass to the next stage of the AC system.

• Receiver/Dryer: Present in vehicles equipped with a thermal expansion valve, the receiver – or dryer – protects the compressor and other parts of the AC system from damage from unwanted particles and liquids. It separates gas from liquid (because the compressor can only handle gas), removes moisture by way of a desiccant, and discards contaminants.

• Accumulator: Found in vehicles with an orifice tube, the accumulator has roughly the same function as a receiver. In fact, your A/C system will have either a receiver or accumulator – not both. In addition to filtering out debris and moisture, this part controls the amount of refrigerant that flows into the evaporator. The accumulator also stores excess refrigerant so that it cannot enter and damage the compressor. If you have an accumulator, then you don’t have a thermal expansion valve.

• Thermal expansion valve or orifice tube: The thermal expansion valve and orifice tube have roughly the same function. In fact, your A/C system will have either an orifice tube or expansion valve – not both. Situated between the condenser and evaporator, either the expansion valve or orifice tube is responsible for regulating the amount of refrigerant that enters the evaporator, greatly reducing its pressure and temperature.

• Evaporator: This component does the actual "cooling" in the vehicle. Set just behind your dash, the evaporator removes humidity from cabin air and cools the air that passes over it. A clutch cycling switch monitors and controls the temperature inside the evaporator’s core to prevent it from freezing, which can greatly damage your AC system as a whole.

• Blower motor: This part moves the cool air that has passed over the evaporator through your vehicle’s vents. It is controlled by a central control head (or resistor) for fan speed. Also in the distribution system are a series of mode doors that control the direction of flow of cold air.

Note that all of these parts are universal for any vapor-cycle AC system, but the way the refrigerant is metered, controlled, and restricted will vary from manufacturer to manufacturer.