With the R-12 used in older cars, and I assume the same is true with R-134a, moisture reacts with the refrigerant and produces acid. The drier has a chemical in it which reacts with and removes moisture. Moisture will slowly diffuse into a fully charged system hence the need for a drier. So, the longer you leave the system open to the atmosphere the more of the drier chemical will be used up. Any openings to the AC system during your repair should be plugged.

The reason they pull vacuum on the system before recharging is to remove air but also to remove moisture. As the air pressure goes down the boiling point of water becomes room temperature and the water boils out. However, if your drier is wet, applying vacuum is not going to fix the drier.

 

Thanks man, I appreciate the feedback about the drier situation, haha. I called a local auto A/C shop and explained my situation and they said the same thing. Just ordered that along with some other parts from Mitsubishiparts.net

Thanks for the input everyone!

 

if you vacuum everything out does it also vacuum the oil out? I had my lower hose get a hole in it and I saw oil also leaked out. Does the machine also replace the oil in the system or is that a different issue? How much oil and what kind if the evac machine doesn't fix it? Let em know, and yes I brought this thread back from the dead, lol....thanks for any/all input on this.