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[grifter]

Bought one of those gauges and gas bottles from 'alfords the other day in an attempt to top up the AC, gauge said charge was under the green "filled" section so gave it a blast of some gas. Compressor clutch started spinning and proceeded to put both temps on low and fans on. Felt a slight difference in cooling to the cabin but not much I must admit, it was paltry really. I was driving all Saturday so let it be and see if it got any better to no avail.

Decided that since I'd been running it all Saturday with only the first refill thought I'd try again tonight with car having been sitting. Again it was just under the filled green section so topped it up again, tried inside fans and while at first it felt like it was getting colder, it then just reverted to kind of average temp again. High line pipe doesn't feel cold, just average.

I am aware of the air con or climate control being influenced by the outside temp in some way but if I slam it on to low for both dash switches should it not give me a blast of the chilled air? Temp outside the now is about 12oC.

[Lizzie Zoom]

I will always recommend that you use a reputable a/c specialist / dealer to refill your gas.

The Halfords kit has been tried by others on here with very mixed results. Most have reckoned it is a waste of money.

The specialist cost is relatively small, so you might as well use them on that score alone.

[Jimbob]

Your gas could be going out (almost) as fast as you add it.  Best not waste any more time and money with those kits.
Get it gassed professionally (check groupon for a 20-30 quid deal) and this should include a pressure test to check its air tight first of all, and dye in the gas so a leak can be found should it have one.  Youre way above ambient cut off temps, think thats meant to be about 2 degrees

[grifter]

Sound chaps, will have a look at getting it tested out by someone, hoped the gas bottle would fire it back into life but alas not!

[Jimbob]

Sorry to say they seem to be generally wasted money, unless for possibly replacing a bit of the 10% annual losses on an otherwise working system....But even then Id prefer to have it done properly for optimal performance

[TheBoy]

Sorry to say they seem to be generally wasted money, unless for possibly replacing a bit of the 10% annual losses on an otherwise working system....But even then Id prefer to have it done properly for optimal performance

Which presumably gets replaced with air, making adding more refrigerant in via silly diy kits a mission doomed to failure...

[Doctor Gollum]

Some crossed wires here... The 'Losses' are a loss of performance rather than a loss of gas.

Surely if there's a leak, it will leak in fairly short order regardless of high or low pressure side.

If the system is still sealed, which I doubt, then topping up using the idiot kit will actually over pressure the system.

Unsurprisingly it then won't work as the pressure sensor measures both under and over pressure and turns it off accordingly.

Also worth remembering that the gas is measured by weight rather than volume... Another reason why the idiot kits are a complete waste of cash

[Kevin Wood]

Indeed. Only way to know where you are is to vac the system out and start again, so you know how much you have charged it with.

[LC0112G]

Sorry to say they seem to be generally wasted money, unless for possibly replacing a bit of the 10% annual losses on an otherwise working system....But even then Id prefer to have it done properly for optimal performance

Which presumably gets replaced with air, making adding more refrigerant in via silly diy kits a mission doomed to failure...

No. Air can only get in if the pressure in the A/C system drops to or below atmospheric pressure (nominally 1 bar).

The AC system is protected by a low pressure (LP) switch which cuts the compressor out if the gas pressure in the pipes drops below (about) 2 bar (30 psi).  There is a second high pressure (HP) switch that cuts the compressor out if the gas pressure exceeds (IIRC) about 8 bar (120 psi). There is also a mechanical 'dump' safety valve on the compressor that will vent the gas to atmosphere if the pressure exceeds another limit - 20 bar (290 psi) IIRC.

With the engine not running, the entire A/C system will sit at a pressure dependent on ambient temperature and the amount of gas in the system - usually 3-4 bar ish. When you start the engine, and the compressor starts, the output of the compressor pumps up to 8 bar, and the input to the compressor drops close to 2 bar. This keeps all the pressure switches happy. However, if you put too much gas in, then the compressor output pressure may exceed the HP switch limit, and the compressor will cut out. On the other hand if there is not enough gas in the system, then the compressor may or may not start. If it does start, the output pressure rises, and the input pressure drops. If the input pressure drops below the LP cut-out then the compressor will stop again.

Due to the high pressures involved (up to 8 bar) A/C gas will escape from the system through the slightest pipework or seal leak. However, air can't start to contaminate the A/C gas until/unless the pressure drops to near ambient. If the pressure is that low, it's unlikely a single can of gas would raise the pressure enough to get above the minimum LP (2 bar) to allow the compressor to start.

All that said, I'd still rather get the system properly vacumed down and re-gassed with the correct mass of refridgerant that try and use a diy kit. And a system shouldn't lose anything like 10% a year. My Carlton was last re-gassed over 10 years ago and it's still working.

[omega2018]

mine lasted just about 4 years before the performance dropped and 5 years before needing a re-fill.  service places recommend re-gas every 2 years (but they would say that woudn't they ).

I think my first mig lasted about 10-12 years but that was from new.