air conditioning blows hot on 2001 Nissan Altima

occasionally, the air conditioning will start blowing hot air instead of cold air. why is this? Had a/c charged but situation did not change. Blows air fine, just not cold all the time.

Asked by for the 2001 Nissan Altima
you need to have this checked by a qualified Japanese
specialty shop. could possibly be a evap temp sensor, but this is just a guess.