AndyRKett one last question I promise: how do the AC shops detect a leaky system or tight system? Is this done when they connect the evacuation/recharge machines to car... The one that pumps in fresh freon/oil? Or is it by a separate test on a different tool? In other words: of I get a seasonal evac/recharge done, would they be able to have ALSO detected whether my system is leaking? Or is the leak test a different procedure? THANKS
I think this has been answered already, but just for completeness.
There are three ways to check for leaks on a system (4 if you could your ears and listening for the gas escaping)
1. connect the recharge machine up. Vacuum the gas out of the system then hold the vacuum for 30 minutes to an hour. If there are leaks then the system tends to lose the vacuum and fills up with air. The draw backs of this method is that the system spends most of its life under pressure so when you vacuum it, things like the seals and the shaft in the compressor can move and let the air in, even when pressurized there isn't a leak. An Aircon specialist I know spent weeks trying to fix a leak on a system on a classic car only for it to be some slight wear in the compressor letting air in, when vacuumed but sealing up when under pressure.
2. There is the fill it with something inert method, like nitrogen. Pressurize the system to full pressure and see if the system holds the gas. Ok for a check when regassing but does not show any slow leaks and a few days after a regas you can still find the system empty.
3. There are electronic "sniffers" machines that have a probe on the end of them that is able to detect the gas leaking out of the system. Can find bigger leaks ok but very slow leaks are harder to find especially in something like the condenser where there may be a tiny pin hole leak that you can't get the probe close enough too. Also affected by the wind blowing the gas away before the probe can detect it.
Sometimes the most reliable method is to had dye added to the system when it is refilled. Then when the gas leaks out the dye will leak out with it. This can then be detected with a UV light. If you have a UV light you could shine it around under the bonnet, the system may have previously been filled with dye and you might be able to find the leak. Best done in the dark as very hard to see the dye glow in bright sun light.
My advice for anyone with air-conditioning in their car is use it frequently. (mine is on all the time in my car when its not broken like it is at the moment with a compressor pulley issue) This keeps the oil circulating around the system, it keeps all the seals supple and will minimize the chance of the gas leaking out over time.
Then if you can avoid it, don't have it regassed unless it actually needs it. As soon as you open up the system and have it regasses it can upset seals and cause leaks that would not have happened if you just left it alone. In this respect the home refil kits are actually good as they don't vaccum the system they just top up the lost gas but should only be used when you know that there is gas in the system and the system is just weak, rather than when the car has lost all its gas and the aircon doesn't work at all.
Finally I'd advise not messing about with aircon unless you know what you're doing. there is gas under extremely high pressure. That can cause severe freeze burns if released onto skin and can suffocate in confined spaces as it displaces all the air. If a pipe bursts it will go with a lot of energy and can cause serious injury.