I had a lot of rejections when I tried a couple of years ago to get my Sera aircon re-charged.
Most specialists and “specialists” refused to do it because they either said the valve was an R12-type so my system contained R12, which was now illegal, and/or they didn’t have the correct adaptor to connect their equipment to the “old-type” valve. Their opinions also varied on whether you should or should not add the replacement gas, R134A to a system containing R12.
As my system had been re-charged by the seller immediately before I bought the car I reasoned rightly or wrongly that my system would contain the correct R134A.
Then, while in Halfords I saw that they sell a D-I-Y aircon recharge kit. And they offer to do it for you at a small charge. So I asked them to do it. They spent some time attempting to do it then said they couldn’t do it because they did not have the correct adaptor.
Based on recommendations on this forum, I bought an adaptor and went back to Halfords. They spent some more time trying to do it, but gave up because the pins in the adaptor would not line up correctly with the pins in the valve. ( “pins” as in the centre pin which tyre valves have and which Sera aircon also has)..
Later, at home, I pondered the problem, and realised that as long as there was a pin in the car’s valve, it didn’t need a pin in the adaptor because the gas pressure would overcome the valve anyway. So I removed the pin and valve from the adaptor. Then I fitted the adaptor to the car’s valve and took it back to Halfords. Now their connector tube screwed onto the Sera’s aircon valve and they successfully re-charged the Sera’s system.
This year my Sera’s aircon system needed re-charging so having seen how Halfords did the job I returned to Halfords to buy their D-I-Y kit and do it myself. I found that they have changed their applicator and instead of the “old”-type screw-on connector their kit now has a clip-on connector, just like a car’s tyre. So my modified adaptor was no longer needed.
Also on Halfords air-con stand I saw that they now have “STP Super Seal - Air-con stop leak”, so I bought some of that as well as a tactical precaution.
Armed with the R134A gas canister and the “Stop Leak” I returned home and successfully recharged my system myself. My car is now as cool inside as its looks are from the outside.
N.B. It is illegal to discharge R12 gas into the atmosphere. An illegal way to check if your car has any gas pressure of any type in its aircon system is to depress the pin in the valve and listen for the hiss.