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[terry paget]

Today in Halfords buying a plug for my lawnmower, I spotted a stand full of kit to recharge my aircon system. Can this work?,

[biggriffin]

It's not worth it, when you can get it done properly for £40.

[tunnie]

Yes, but you need to know how much is in there/what goes in, some don't appear to come with a gauge.

These cheap kits also don't allow a pressure test, a garage will vac the system and pump a clean air in, to pressure test the system for leaks, before putting in the real gas.

Worth going to a proper place really in my view.

[biggriffin]

Yes, but you need to know how much is in there/what goes in, some don't appear to come with a gauge.

These cheap kits also don't allow a pressure test, a garage will vac the system and pump a clean nitrogenin, to pressure test the system for leaks, before putting in the real gas.

Worth going to a proper place really in my view.

There corrected, don't want anything going bang,.

[Lazydocker]

Errm... I don't think they pump anything in, they just vacuum it out and see if it holds the vacuum

[biggriffin]

Errm... I don't think they pump anything in, they just vacuum it out and see if it holds the vacuum

Proper air con people should de-charge system, then pressure test with nitrogen(25psi) see if it holds and to check for leaks, then re-vac, allow to hold vacuum for 20minwets, then re-charge.

[Tony H]

Not worth the "hit and miss" chance taking the DIY route for the sake of £40 to have it done by a specialist 

[Scatmancraig]

I've used the Halfords stuff before a few years back.  Was useful to top up the air-con in my old BMW 530d, the system worked just not quite as cold as it should have been.  I did a similar top-up on my old 2.3TD engined Omega, as that car had a leaky valve.  I probably wouldn't use it to top up a car that has no gas in it though.

[Kevin Wood]

Yep, they are absolutely useless if the system has no gas left, as you have no way to vacuum out any air and moisture in the system. You also have no way of knowing whether you've got the correct mass of refrigerant and oil inside. Even with a gauge, you're guessing, because once the vapour pressure of the refrigerant is reached (which changes with ambient temperature) the mass of refrigerant has little impact on the pressure.

It's not really viable on a DIY basis unless you have a decent vacuum pump and can weigh the refrigerant in.

[Nick W]

It would be a way of making a leaking system 'work' long enough to sell the car.
Otherwise, why would you bother? It's not even any cheaper than doing it properly.

[Lazydocker]

Errm... I don't think they pump anything in, they just vacuum it out and see if it holds the vacuum

Proper air con people should de-charge system, then pressure test with nitrogen(25psi) see if it holds and to check for leaks, then re-vac, allow to hold vacuum for 20minwets, then re-charge.

Learn something new every day... I've never seen/used or even heard of using Nitrogen. I know that I've never seen a machine capable of using it either, just vacuum it and hold for the test

I know they used to use Nitrogen for testing about 15-20 years ago and it is still used to purge a system before working on it but never seen it in the modern age

[Entwood]

When I replaced the compressor last month the guy vacc tested it for  10 minutes, then filled with nitrogen to 9 bar for 20 minutes, before vaccing again, this time with a hot air stripper pointing at the filter/dryer before refilling with gas/oil.

His reasoning when asked .. initial vac test is simple way of checking for major leaks, but the system works under positive pressure, not negative pressure, so the nitrogen test is a "true" test of system soundness as the vac test can "suck" a seal in and make it work when under the "blow" of pressure it actually leaks. final vac with the hot air gun on the filter/dryer ensures all moisture/vapour is removed from the system prior to refilling.

I don't know enough to argue but the logic makes sense, even to me ..

[Lazydocker]

When I replaced the compressor last month the guy vacc tested it for  10 minutes, then filled with nitrogen to 9 bar for 20 minutes, before vaccing again, this time with a hot air stripper pointing at the filter/dryer before refilling with gas/oil.

His reasoning when asked .. initial vac test is simple way of checking for major leaks, but the system works under positive pressure, not negative pressure, so the nitrogen test is a "true" test of system soundness as the vac test can "suck" a seal in and make it work when under the "blow" of pressure it actually leaks. final vac with the hot air gun on the filter/dryer ensures all moisture/vapour is removed from the system prior to refilling.

I don't know enough to argue but the logic makes sense, even to me ..

I suppose my experiences are based on garage machines rather than an Air Con Specialist