Automotive Air Conditioning Information Forum

When charging an empty system that has been vacuumed, is it ok to charge liquid into the high side with the system off and then close the high side and add the rest of the charge as gas to the low side?

Yes.

Especially when faced with multiple cans.

Drop the entire first can in the high side under vacuum with the can tap & high side valve wide open.

You usually only get one can in this way, but you have enough initial charge to make the system cycle & return oil. Close the high side valve & then start the engine & begin charging through the low side as gas, at idle.

If you are charging from a scale with a tank, you can usually get most of the charge in this way. Saves time.

Always charge liquid in to the high side. Blasting liquid through the compressor when stopped can remove the lubricant from the cylinder walls & damage the compressor. This is especially true on systems where the low side port is a couple of inches from the compressor head.

Thanks! This will be a real time saver. I work at a small town fire department and was working on a truck yesterday. It takes over 5 lbs. takes a long time to charge through the low side only.

As a real example a system recently was spec'd to take 700 grams (max fill) of refrigerant. Connecting liquid to the high side under vacuum we were able to charge 420 grams before switching to low side gas charge with the engine running for the remainder.