air conditioning problems 93 ES300

Hi,

I am new to this forum and I need some information on air conditioning for a 1993 Lexus ES300. The air conditioning keeps changing from cool air to regular circulated air. Doe this mean it needs new chemicals? Also, does anyone know if this car uses the old air condition systems or the new system? We purchased this car last year and put a transmission in it and we really like it, but we are now having air conditioning problems. Thanks. J Mac