I installed, serviced, repaired, and trained the users of these machines in Kwik Fits in the south of england a couple of years ago.
It runs through an automatic cycle, advancing to the next when certain criteria have been met.
It checks for positive pressure in the system, if it sees any it will zero it's internal gas bottle scale, and zero the recovered oil bottle scale. Recovery starts, and when it sees a pressure of minus 0.2 bar it stops the recovery and waits for a couple of minutes. If it see pressure rise above zero, it restarts the process. When it sees no pressure rise, it opens it's internal oil seperator into the waste oil bottle for 30 seconds. After that it records the weight increase in its gas tank and oil bottle.
Then it starts the vacuum process for the preset time, usually 30 minutes. After this it monitors the pressure again for a couple of minutes. If it sees a pressure rise of more than 200mbar, it fails the leak test. But.... measuring pressure increase from a vacuum is a poor method of leak testing, as you've only got outside air pressure trying to get in. So this test is generally meaningless unless you have a large leak.
If it passes the 'leak test', it will open up it's 'new oil' bottle to the system and the vacuum in the system will draw in oil until the bottle weigh scale has changed by the correct amount (ie, the amount that it weighed out in the previous oil bottle). After this it refills the system with liquid refrigerant from it's internal tank as set by the vehicle database in the machine. It automatically adds a small amount extra to account for what stays in the charging hoses. When disconnected from the car, it will then recover the charging hoses so they are empty for next time. Then you get a little printout showing - gas recovered, oil recovered, pass/fail leak test, oil charged, gas charged.
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