Is it R134 in Halfords AC charge bottles or something else that is compatible with R134 but not regulated (regulated as in should only be supplied to AC pros?
And if it's something else is it as good (efficient etc) as R134?
IIrc Sloth or someone else once said it wasn't R134 in Halfords bottles? At the time I thought there was R134 in them (thought I'd read it on the side of the bottles) but now it's been said it's technically illegal to supply R134 to none pros I wonder again if it is R134 or something else.
Like Sloth I too have never known an AC machine pressure test, only vacuum test, and have known pinprick holes seal under vacuum only for refrigerant to leak out when the system is pressurised. But then again I won't have seen as many AC machines as an AC pro.
What I have done is pressurised an AC system myself just using compressed air to check for leaks (see if the system holds pressure), I know it shouldn't be done and moisture in the air could mess up the dryer (and/or other parts?) but rather than waste an hour at Kwik Fit for an AC system to pass a vac test then leak refrigerant when I drive away (so I have to return for money back - they give a 2 week guarantee even if the system leaks) I've done this when I've suspected a pinprick hole that might seal under vacuum.
I have a few Halfords AC recharge kits, at least one intact, at least one I've cut up so I can connect an air compressor to the LP port. I wouldn't gas up an AC system from flat using a DIY kit (partly because it's cheaper to let Kwik Fit do it and the Kwik Fit guarantee) but when I have a car that takes 0.995 kg of refrigerant and I see the Kwik Fit machine only wants to put in 0.85kg of gas when my reg is entered I have to wonder if the AC system would benefit from having a bit more gas than the Kwik Fit machine puts it (even though I tell the operator to manual over-ride and set the machine to 0.995kg) because I wonder if the vehicle manufacturer knows it should really have more than 1kg of gas in it but there might be some sort of environmental threshold at 1kg - Indeed Kwik Fit charge a lot more (iIrc double their usual fee) to charge an AC system that takes more than 1kg of refrigerant. The Halfords kits come with a pressure gauge that you set according to ambient temperature, the instructions say charge with gas until the LP port is at a certain pressure when the clutch is in... but machines don't do this kind of operational test (or operators don't do the operational test) ? On a few makes/models after having an AC machine fill I've found that the AC system gets colder with the engine at idle if I put just a but more gas in it from a DIY kit... Got to wonder if the machines short-change on the weight of gas they measure they're putting in?
Years ago before AC became as popular in the UK and systems were mostly R12 if you spoke to an AC guy they'd be reluctant to regas a system without changing the dryer. Most of them didn't have machines and couldn't do a vacuum purge/test, you just parked on the street outside their house and they'd come out with a camping gaz size green bottle and connect it to the LP port... with enough pressure the AC clutch would kick in and pull the gas into the system while they watched the sight glass and filled it til there were no bubbles.