My air conditioner on my 2001 rx300 Lexus IS blowing hot air. Compressor works , fan works, and last summer it did the same thing. I asked service person to put freon in and was told that it was

It sounds as if you have a leak in the system. The leak will need to be repaired and recharged. It may be easy to find and then it maybe hard to find, it all depends on where the leak is (High or low side). The best way is to put in a dye into the system determine the location but may take a day or so for the dye to work its way to the area where its leaking. If you need the car and cant wait go to a local auto store and purchase a can of refrigerate the one with the gauge indicating that the system is full. But know that the refrig will leak out again until the leak is found.

Sounds like you have a leak in the system. Hear is something you can try no promises but it worked for me add a can of R134a refrigerant leak sealer. Add no more then one can if it does not work do not add any more hoping it will seal it will clogg the system. Have system fixed if does not work

you have a leak