Vehicle a/c systems are filled with a specific amount of refrigerant from new, similar to your fridge/freezer, the only difference is that in a vehicle system there needs to be flexible hoses to accomodate relative movement between the engine and chassis. Over a period of time some of the refrigerant leaches out of these hoses or a weak point in the system and it will cease to work efficiently. With most ‘European’ vehicles this usually occurs around 2-3 years, Japanese vehicles often last a little longer.
As the refrigerant level drops the cooling efficiency becomes less, until a pre set piont where the low pressure switch opens to prevent the compressor running ‘dry’ and self destructing.
No vehicles have a ’sealed’ system all vehicles have charging points, these are used to monitor the pressures and recharge the system when required.
If the system is found to be empty then it will need to be leak tested and the leak repaired, but if there is some refrigerant left it will simply need recharging, which should cost around £50.00 depending on your location.
It is better to use a specialist who understands the system, DIY kits are rarely effective for long and cost almost as much, added to which it is now illegal to handle refrigerants without the correct qualifications.
Bob. R (
http://www.caraircon.co.uk )