Strange things are happening with my air conditioning system.

It started blowing hot air...I live just outside of Phoenix...I bought a case of R124 at Sam's Club and re-charged the system.

Here's the strange part. It blows cold for a day, a week and then it blows hot again. Sometimes it does it the next day, but always, while the car is running the air is ice cold.

Can someone tell me where the most likely place for a leak would be?

Also, is there some type of lubricant that is embeded in the R-124?

Thank you for your words of wisdom.