On the 3rd of this month I enquired here about using a kit on my E39.
I'm not suggesting that any of the advice I received from my original was bad. If one can afford it, there's no doubt that having a competent A/C professional do the job is the better way to go.
My system was working but not cooling as well as it should. My guess was that it had simply lost a little gas since it was professionally regassed about 3 years ago.
Looks like I was right. Bought a kit for £30 and used it today, and am well pleased with the result. A/C appears to be as cold as it was when it was regassed properly.:-)
After connecting the hose and guage to the A/C low pressure port and saw the pressure was only down about half a bar or 7psi, I thought I might have wasted my money, but carried on and opened the valve on the hose to allow gas from the can into the system. Guage went from 2 bar to 2.5 bar, but very little gas appeared to come out of the can of gas. It felt almost as heavy as it had before I'd opened the valve, so I presume it needed very little gas, in terms of weight, to top-up the system, but it was obviously enough. Getting back into the car with the A/C running at it's lowest setting, the air coming from the vents was very cold.
Well pleased with result. A significant saving of £40, as the cheapest professional regas I could find locally was £70.
The can of R134a gas supplied with the kit has PAG oil added in case any wonders about the affect that adding pure gas might have on the system. Mike.