Management won't fix the A/C unit

[Melissa52]

We have lived in this apartment in Missouri for almost a year. Last summer the air conditioning was not efficiently cooling the apartment (it would stay anywhere from 80 to 90+ degrees during the day). We called 3 times about the problem last year and we were told the same thing - its working fine. The problem has started again this year and I can't live another summer like that. They sent out a maintenance guy out today to look at it and again the same response - its works just fine, you're just in a bad spot. I talked to the apartment manager and she wouldn't be direct, but basically told me they won't do anything about it except check the insulation above the apartment, and even if thats a problem, fixing it will only make a difference of a few degrees. My lease doesn't say anything specific about air conditioning. Do they have to do anything about it? Do they have to replace, repair or even upgrade so that our apartment is efficiently cooled? Can we sue? Would it be worth the trouble?