All vehicles have different amounts of oil and refrigerant gas, too little and it wont work, too much and it wont work. So with these cans that you can buy, do you know how much gas is in the system...
With the Air con machines, they drain all the gas and oil out of the system and drain the moisture from the Air con dryer, and it also checks for leaks (Vacuum check) then it puts in the right amount of oil and gas...
What I don't understand is that I had to do an exam and practical test for my Air con licence, as you have to have a licence to handle the R134a refrigerant gas, so what happens if you have an accident with these refill cans
as you can still get frost bit from the gas if it contacts your skin....