2003 MITSUBISHI LANCER User Comment / Complaint

After purchasing my vehicle i noticed two things, one that is troublesome and the other a major inconvenience. one day after stepping out of my vehicle while the vehicle was running with the a/c on i heard a loud rattling sound every time the a/c kicked on. i took it into a dealership while i was having them check my temperature control knob (the other problem) and told them about it. they just put grease on the knob and told me that the a/c is supposed to sound like that. well, just this last fall my a/c compressor (i think it is the compressor) blew out and started smoking. i thought that the freon was empty but it is not. is this legitimate for a complaint?