If you take it to Kwik Fit for a regas they will do all the tests first before they actually try to fill it with gas,by evacuating the old gas then pressure test and only if it has no leaks will the machine refill the system,oh and they also put in a dye to see if there are any leaks and if there are any problems during the process you are not charged,as i said Kwik Fit are good for this service,just about anything else not so good...oh and i don't work for them either.