Is an air conditoner broken it if will not get the house cooler than 75 degrees?

What you really want to know is: What's the temperature of the air coming straight out of the air conditioner vent ? It's easy to stick a thermometer into the louvers while the unit is running, and see what it's putting out. I'm not sure what it should be, but definitely less than 55 or 60 degrees ... there's no way it can ever make the house cooler than the air that's coming out of it, and if it's like 70 degrees coming out of the machine, then it'll take all day to bring the house down to 75. -- One thing you always want to make sure is that it has a clean air filter in it. Either clean the one that's there, or replace it with a new one. If the filter was clogged, that alone could be the problem. -- The job of the air conditioner is to blow cool air out. But every air conditioner also needs a way for air to get IN, so it can cool the warm air and blow it back out. Find where the air intake is, and make sure it's not blocked or covered. Most likely, the air intake is immediately outside the filter. -- If the air coming out is not cool, then the air conditioner has a problem and needs work. Best case, it just needs its refrigerant re-charged. Worst case, the compressor or radiator is failed. You might be able to identify the problem, but you can't fix any of these. Call in a pro.