Hi jd620,

Let the tank stand upright. This for vapour charging with engine ON and AC ON (i.e compressor ON).

Since you have mentioned about inverted tank I had tried a few times doing liquid charging by inverting the tank. Much faster. All done in about 5 minutes. But in this case engine must be OFF and ONLY for charging from ZERO/VACUUM. Put the inverted tank on the weighing scale (I use digital), zero the reading then open the BLUE valve. Monitor the rapid weight reduction at scale until nearly 900gm. Shut BLUE valve immediately. Now open BLUE valve slightly to SLOWLY add another 50gm. Stop. Wait a few minutes for the liquid R134a to turn into vapour in the BLUE hose and the system. Disconnect BLUE hose from low pressure port, START the engine and AC.

Liquid charging is possible but you must pay VERY close attention to the scale. This method of charging is VERY FAST. Compressor must be OFF (it can't compress liquid). Also arrange the YELLOW hose routing from the inverted tank so that it doesn't add FALSE weight to the scale. Important to allow some time for the R134a to fully turn into vapour before starting the AC. Finally charging must be done in warm weather (i.e about 70F and above) so that all could turn into vapour.

Liquid charging is normally done for home AC where large amount of refrigerant must go in (e.g 2000gm to 3500gm). Another reason for liquid charging is when the refrigerant is a mix of 2 different refrigerants in that when doing vapour charging they might separate unequally leading to improper charge. Again this is mainly for home AC.

Sorry for the long story. Just to share some info and perspective.

Regards,
Amarin.