That is indeed true but not likely unless the system has been completely opened or air was forced into the system.

 

I agree, it's a sealed system but not full proof ortherwise there would be no need to recharge the system. If refrigerant seeps out there is a empty cavity somewhere in the system, you could see air in the system with the old sight glass systems. there is no way to know how much is gone so we go away from measuring ounces and use PSI as the standard to top off the system, not very accurate but what the heck, it's almost as cold as last year. After the air in the system turns to condensation from temp changes in the system corrosion starts occuring. Evacuate/recover is the only correct way to service an air conditioner.

 

Its still NOT air. In the old sight glass systems it would be freon vapor bubbles that pass thru the sight glass

 

On and average day, 75-80 degrees the low side will be 35-40 mercury PSI the high side should be 200-250.

 

I hope now that it has been 9 years that they figured out how to charge the system. That or they moved to northern Canada and said screw the AC.