Automotive Air Conditioning Information Forum

For 30 some years I've charged as a gas into the low side because that's how it was done. Now I've read a few members here who say to charge liquid thru the high side with engine off, then top off on low side if needed when running. Do I have to wait for the system to stabilize before going to the second phase if needed? Want to avoid slugging the compressor if any liquid has reached it.

I think the others will agree this is a procedure for the pros only. Slugging is always a concern.
However, if you are experienced, and if you truly know the exact weight specified, and have a reliable refrigerant scale, you can charge the full amount as liquid thru the high side with the engine off of course. You will have the cylinder upside down to do this. How do you think they do it at the factory?
With this method you will not be charging any vapor. You will also have the best startup that is possible because the full amount of refrigerant will be in the system to start distributing the oil, ie the comp will not lack for oil. Done exactly this way, you will not slug the comp.

This calls for a system that is tight and in good shape, prolly best cleaned back to bare metal. Few of us ever gets the chance to charge a totally new and clean system the way the factory does.

On custom systems without known charge weight, I will sometimes allow an entire can (12 oz) in as liquid, and then finish off by vapor from a 30 pounder, but you have to know what you are doing.
The bottom line is there is more than one way to charge

Well, I was able to get 1 lb 8 oz through the high side as a liquid and then it stopped. Turned the drum right side up and got the remaining 8 oz in through the low side with the engine on. Surprised how little time it all took. Might do it this way from now on.

Slugging happens more when the gauges are connected to the compressor itself. I always have, and most will charge as a liquid unless I'm using an R & R machine. But there is a concern when charging as a liquid. SO be gentle; no need to open the gauges wide open right off the bat when charging.