I wouldn't advise anyone to use the DIY kits if the system wasn't already partially charged - for starters it wouldn't be worth it because you'd need a couple of bottles for a complete charge and that'd cost more than a pro's price, so I think with the air and moisture points factored in the pro method becomes a no brainer for anyone who's had a holed R132 system unless it'd be too inconvenient to visit a pro... but for a top up the bottles can work out cheaper and be more convenient, probably get a few top ups out of one bottle. In these parts Charlie Brown's (there's a chain of them) regas on a no improvement no fee basis, they measure before and after vent temps and if after temp isn't at least a degree colder you don't have to pay. I had a similar discussion to this with my son the other day, his old Mondeo's AC was working a bit but not nearly as well as it had last summer and he reckoned he could tell it wasn't dehumidifying the cabin, he decided to pay £45 for Charile Brown's to do it after considering that his system was probably holed for a long time until he fixed it (scrapyard compressor, condenser and dryer) last year, so a complete discharge and recharge might help clean any crap out of his system and swap some oil for new. However, I did charge the ML up from so low the clutch wouldn't engage using a DIY bottle because I bought the ML at the last minute before using it to go on holiday and didn't have time to visit Charlie Brown's.. One bottle got it working, though I knew one wouldn't be enough to properly fill it. Simple test before attempting to charge that'll at least tell if the system is attempting to hold pressure, see if there's any pressure in the system by depressing the valve on an AC port, easy test to see if the clutch is going to work is to wire it straight to battery, can then tell if the pump is seized or noisy... Only bits now without having had a rudimentary test are the pressure switches, heat sensors and control electronics.
I had the Granada with AC in 1990 when I was 19/20... Back then it was almost unheard of for cars to have aircon except for the likes of prestige stuff and Yank imports, maybe around 1% of mk2 Granadas will have had it. I knew the theory on how it worked but there was no internet, little info available on the subject, main dealers quoted ridiculous prices, indi-pros mostly worked on office AC and didn't know what parts the mk2 would have without 'Bring it in, we'll have a look and probably have to adapt a dryer and pipework to suit, you definitely need to change the dryer or it won't work', any part of at a silly price. I think a lot of people back then didn't know what AC was all about, the term could give the impression of clean air not necessarily cold air, even people who knew it cooled the car probably wouldn't have expected it to cool it by much unless they'd experienced it.. I remember it being an unknown to my mate until a few years later when he got in my AC'd Scorpio, then he said his next car would definitely have it. I wish I'd known a bit more about AC in 1990, especially that propane could substitute R12... Can picture myself rigging up something to try to purge the system of air, maybe bleeding lots of propane through the system while the engine bay, vehicle interior and all AC piping was hot... I would have thought that would just about cover it just leaving the filtering in question, but I'd have rather just trust the existing filter than fork out a few hundred quid in 1990 to change it, reckon filter would still filter even if the bit that takes up water was knackered? I'd probably take the same route today on an R12 system because few AC pros seem geared up to work on R12 these days?
I fixed an R132 system that had a corroded alloy pipe on a Pug306, was corroded by electrolysis where it attached to the metal front cross member and would have cost a fair bit of money and time to fit a new pipe because it was a long one that ran all the way through the bulkhead (dash out job). Fixed with a flexi pipe I had an hydraulics firm make up, proper AC fitting at one end to connect to the condensor but just a bare pipe at the other end with several J clips holding it onto the alloy pipe I'd cut short. Was still working 3 years later when I sold it without being recharged in that time.
