Air conditioning


In a vehicle air-conditioning system, the refridgerant is circulated under pressure through the five major components, in a closed circuit. At these points in the system the refrigerant undergoes pre-determined pressure and temperature changes:

  1. The COMPRESSOR takes in low pressure refrigerant gas through the suction valve (low side) and as the name indicates, pressurises the heat-laden refrigerant and forces it through the discharge valve (high side) on the condenser.
  2. Ambient air passing through the CONDENSER removes the heat from the circulating refrigerant, resulting in the conversion of the refrigerant from a gas to a liquid.
  3. The liquid refrigerant moves on to the FILTER/RECEIVER DRIER where impurities are filtered out and moisture removed. This component also serves as a temporary storage tank for the liquid storage for the liquid refrigerant.
  4. The liquid refrigerant, still under high pressure, then flows to the EXPANSION VALVE/TUBE. This valve/tube meters the amount of refrigerant entering the evaporator.
  5. As the refrigerant passes through the valve/tube it becomes a low temperature, low-pressure liquid and saturated vapor. The low-pressure liquid immediately starts to boil and vaporizes as it enters the EVAPORATOR. The hot, humid air is drawn or blown through the evaporator by a fan. Since the refrigerant is colder than the air, it absorbs the heat from the air, producing cool air, which is then pushed into the interior of the vehicle. The moisture in the air condenses upon the evaporator (thus dehumidifying/drying the air) and then drains out of the car.


The cycle is completed when the heated low-pressure gas is drawn into the compressor through the suction side. 


On most systems the evaporator is integrated into the heater box. This means the air-conditioning can be used all year round (to cool down the inside in summer and provide dehumidified / dry hot air in winter). The only time it is not giving you any benefits is when it is below zero outside.

To get dehumidified hot air, turn the air-conditioning on and set the heater controls to hot. This will create a nice dry atmosphere inside the vehicle and de-mist the windows very quickly. For instant de-misting, direct the air on to the windscreen. Once the windows are clear, direct the air to where you prefer.

For vehicles fitted with re-circulation control: switch to re-circulated air for fast dehumidification, rapid cooling or to avoid fumes, smoke etc. If smoking in the vehicle, make sure the re-circulation control is in the fresh air position. On long journeys, switch to fresh air for a few minutes every hour or so. After stopping your vehicle, you may often find a pool of water under the vehicle if you have had the air-conditioning on. This is a normal occurrence and is a direct result of the dehumidification process.


If possible, park your vehicle in the shade on sunny days. If your car is parked in the sun on a hot day, the inside temperature may reach 70 degrees C. In such case, turn on the air-conditioning unit and drive for a few minutes with the fan on maximum and windows open, for quicker cooling. Close windows after a few minutes.


Air-conditioning reduces both the temperature and the humidity in the passenger compartment. It can provide a comfort level of 50% humidity when the ambient is 70% humidity. Health considerations indicate the most suitable inside temperature is when it is 5 or 6 degrees lower than outside.

For additional information on factory systems, please refer to the owner’s manual.

Please do not hesitate to contact us if you require any further information or assistance.



Vehicle air-conditioning systems have a filter/drier or accumulator fitted. This component has a dual function. It has a desiccant to remove moisture from the gas and acts as a filter.

It is very important that air-conditioning systems are kept 100% dry. Moisture in the system will turn to acid and cause harm to many components.

The filter/drier or accumulator should be changed every 2 years, or whenever the system has been open to the atmosphere for any reason. Immediately after the drier has been changed, the system should be dried with a high vacuum pump.

Vehicle air-conditioning systems can lose up to 15% of refrigerant annually through natural seepage via the system hoses, which will result in poor performance.

Contact our service department if you are experiencing insufficient cooling or you feel that there could be a problem or leak with the system. Have your air-conditioning serviced once a year, to ensure maximum performance and trouble-free operation.

Operate the system at least once a week for few minutes, to keep the compressor shaft seal lubricated. Failure to do so may result in the refrigerant leaking past the seal. If the system is left unattended with a refrigerant leak, rust may develop on the internal parts.


Lack of coolant will cause engine overheating. Check the coolant level regularly. Replenish if necessary with antifreeze and water. If the radiator level tends to drop often, have the cooling system inspected for leaks by a specialist. Most vehicles fitted with air-conditioning constantly require antifreeze in the cooling system. Failure to keep the manufacturer’s recommended amount of antifreeze in the cooling system may lead to the heater matrix freezing and developing a leak.


If excessive engine overheating is experienced whilst operating the air-conditioning. DO NOT use the air-conditioning until the vehicle has been examined and the cause of the problem is rectified.

Our service procedure consists of:

  1. Discharging the system.
  2. Checking the oil level in the compressor (when recommended by manufacturers).
  3. Changing the filter/drier/accumulator if required (normally every two years or when the system has been opened for any reason).
  4. Evacuating the system with a high vacuum pump to remove moisture.
  5. Inspection of drive belts, condenser, pipe work and wiring. Any defects reported.
  6. Recharging the system.
  7. Making sure that the compressor, clutch, expansion valve, pressure switches and fans all work correctly. Any defects reported.
  8. Checking and cleaning the condenser and any other components that require cleaning.
  9. Check that all bracket bolts are tight and those refrigerant hoses, radiator hoses and wiring are not chafing and are in good condition.
  10. Check all belts for wear or looseness. A slack compressor belt may cause poor cooling. The deflection of compressor belt pulleys should be 6 to 7mm. (Approx. 1.25 inches).

Air Conditioning Company Service Policy

Until now you may not have been aware that your car’s air conditioning needed servicing or just assumed your garage included this as part of your normal annual service, but now that you have a problem with your air conditioning we will correct it for you via the following methods…

  1. We will recover the refrigerant (if there is any) from your vehicle’s air conditioning system and evacuate it to remove any moisture.
  1. We will pressure test the system using nitrogen to find any leaks. If a leak is detected (causing the pressure to drop) we will advise on the cost of rectifying the problem and our fee at this point will be £30.
    Examples of common problems include…


    1. Pipe repairs ranging from £20 to £120 to supply + fit
    2. Replacement condensers from £150 to supply + fit
    3. Replacement compressors from £250 to supply + fit


  1. If your air conditioning system appears to be leak free we will recharge it with the correct amount of R134a refrigerant and oil and also add a UV dye.

The cost of this full system service is £45 plus vat takes approximately one hour.

  1. If your system subsequently develops a fault (which is common once a previously un-used system is used again) we can identify the fault easily using a UV dye-light to show any areas where the dye has escaped and again advise on a price for the necessary work.


  1. We will do our best to accommodate your needs with regards to the timing of your service – we have a comfortable waiting room or alternatively you can drop off your vehicle and collect it later in the day.