CARSTARS Garage car A/C system repairs in Dubai Al Quoz

Receiver replacement A/C repairing Dubai

At a certain temperature and a certain pressure, the cooled refrigerant condenses and turns into a liquid state. From the bottom, the refrigerant leaves the condenser and in a liquid state enters the receiver-drier, which consists of a receiver and a drier, installed on the condenser outlet pipe before the evaporator. The receiver-drier performs multiple functions, including storing the refrigerant, filtering it, and removing moisture. Sometimes, the filter is installed separately from the receiver. Moisture elimination is achieved by utilizing a special adsorbent with a limited service life.

Receiver 5 serves to smooth out fluctuations in the refrigerant flow.

Pic: Receiver-drier:

1 – Supply of refrigerant from the condenser; 2 – supply of refrigerant to the pressure reducing valve; 3 – drier; 4 – mesh filter; 5 – receiver

Drier 3 removes moisture that has entered the refrigerant circuit during installation or from the environment, as well as deposited wear products of compressor parts, dirt that got into the circuit during installation and other foreign impurities. The receiver-drier can be equipped with a sight glass to monitor the amount of refrigerant. In case of failure, the receiver-dryer is not repaired and must be replaced.

Pressure reducing valve replacement Dubai

After the dryer, the refrigerant flows to the pressure-reducing valve. The pressure-reducing valve in front of the evaporator lowers the pressure of the liquid refrigerant, which causes the evaporator to cool. The pressure-reducing valve is located at the boundary between the low and high-pressure sides of the refrigerant circuit. The valve regulates the flow of refrigerant to the evaporator, depending on the temperature of the refrigerant vapor at the outlet of the evaporator, therefore, the evaporator evaporates as much refrigerant as is necessary to maintain uniform “cold” in the evaporator.

If the temperature of the refrigerant leaving the evaporator rises, the refrigerant expands in thermostat 4, which is installed on the pressure reducing valve. In this case, the diaphragm 3 bends and the flow of refrigerant through the ball valve 2 to the evaporator increases.

Picture: Pressure reducing valve:

1 – Adjusting spring; 2 – ball valve; 3 – membrane; 4 – thermostat with sensor tube and refrigerant

If the temperature of the refrigerant leaving the evaporator decreases, then the amount of refrigerant in the thermostat decreases, and membrane 3 returns to the upper position. Refrigerant flow through the ball valve to the evaporator is reduced.

The thermostatic expansion valve operates under three forces:

• The 1st pressure in the sensor tube depends on the temperature of the hot refrigerant. This pressure acts as releasing force (PFu) on the diaphragm.
• 2nd evaporator pressure (PSa) acts on the diaphragm in the opposite direction
• 3rd control spring pressure (PFe) acts in the same direction as the evaporator pressure

The pressure relief valve sprays the chilled liquid into the evaporator.

Car A/C Evaporator repairing in Dubai

The evaporator speeds up the evaporation process. For this, it has a large surface area and acts as a heat exchanger between the refrigerant and the ambient air. The refrigerant that has passed through the pressure reducing valve, becoming volatile with low pressure, when passing in a foggy state through the aluminum evaporator pipeline, under the action of the airflow from the fan, evaporates into a gas at a temperature of -2°C and a pressure of 2.0 kg/cm2. In this case, the fins of the evaporator pipe become cold from the heat of vaporization, and the air inside the car becomes cool. In addition, the moisture contained in the air turns into the water from cooling and, together with the dust, flows through the drainpipe into the condensate pan and then onto the ground.

Car A/C Compressor replacement in Dubai

Piped refrigerant in its gaseous state goes to the compressor, which is driven by the motor shaft. The compressor increases the gas pressure to a high level. A clutch, powered by the crankshaft pulley through the drive belt, drives the compressor. When the clutch electromagnet doesn’t receive voltage, only the compressor clutch pulley rotates, while the compressor shaft remains still.On the other hand, when voltage activates the magnetic clutch, the clutch’s disc and sleeve move back and establish a connection with the pulley. The forces cause the pulley and disc to merge, resulting in the rotation of the compressor shaft.

Climate control compressors are of various types:

• piston chargers

• spiral chargers

• vane chargers

• swashplate axial piston blowers

• driven by an electric motor

Compressors with variable displacement axial piston types are the most widespread for air conditioning systems.

Picture: Scheme of a variable displacement axial piston compressor with a rotating swashplate:

1 – Runner; 2 – electromagnet; 3 – swashplate; 4 – piston; 5 – pump cylinder block cover; 6 – valves

A swashplate is connected to the drive shaft of the compressor, which during its rotation moves several (5…7) pistons. A cover with a valve system closes the body containing cylinders. The capacity of the compressor is determined by the desired cooling temperature. With these compressors, the inclination of the washer can change, which leads to a change in the piston stroke and, therefore, in the capacity. These types of compressors exert less impact on the engine operation when the clutch is engaged, which is particularly crucial for low-power engines. In addition, they provide greater stability at the set temperature.

The compressor, depending on the frequency of its rotating shaft, converts the gaseous state of the low-pressure refrigerant coming from the evaporator into a gas of high temperature and high pressure (80°C, 15 kg/cm2). The gaseous state of the refrigerant is necessary for the compressor because the liquid refrigerant cannot be compressed and this would destroy the compressor. The compressor seals the refrigerant and pumps it as hot gas into the condenser (high-pressure side of the refrigerant circuit).

Therefore, the compressor is separation place of the low and high-pressure sides of the refrigerant circuit.

In conclusion

A special compressor oil circulates throughout the system, providing lubrication to the compressor alongside the refrigerant. Systems using R12 freon employ mineral oils (with R134a, polyalkylene glycol (PAG) oils). If these oils are mixed, they form a cloudy, thick mass that can cause the air conditioning system, particularly the compressor, to fail. When adding refrigerant and oil to the air conditioner, it is crucial to use components specifically designed for this system. As a rule, there are stickers in the engine compartment of a car. They are indicate the type of refrigerant, its amount and the corresponding type and amount of oil (stickers for R134а are green, for R12 – yellow).

Car A/C Condenser repair in Dubai

From the compressor, a hot gaseous refrigerant with a temperature of about 50…70°C is supplied to a condenser, which serves to convert the gaseous high-temperature refrigerant coming from the compressor into a liquid state by releasing heat into the atmosphere. The condenser comprises curved tubes that connect with baffles and possess a large cooling surface, enabling high heat transfer. The condenser tubes and louvers absorb the heat from the refrigerant.

The refrigerant in the condenser generates heat based on the heat absorbed by the evaporator from the environment and the operation of the compressor to compress the gas. The cooling effect of the refrigeration unit depends on how effectively the condenser dissipates heat. That’s why car manufacturers usually install the condenser at the front of the vehicle and actively cool it using the air from the engine cooling fan or an additional fan, as well as the airflow created when the car is in motion. Cold outside air flows through the condenser, absorbing heat and cooling the refrigerant.

Car A/C Pressure Sensors replacement Dubai

The air conditioning system features pressure sensors 5 and 7, which prevent the system from operating when the refrigerant pressure falls below a certain value.. To control the temperature regime of the system, temperature sensors 8 and 13 are provided.

In hot local climates, no car is complete without air conditioning. Some cars feature a dual circuit for the rear passengers, adding complexity to the system but enabling independent temperature control for the rear occupants, separate from the front ones. The most common problem is compressor failure or freon leakage. Both through the valves and through the evaporator, the replacement of which sometimes results in a pretty penny for the car owner. In our garage, we carry out any work with the air conditioning and heating system with a guarantee of diagnostics and quality work.