If your AC unit turns on but doesn’t cool, check your thermostat to be sure that it is set at the correct temperature. You should then check the condenser and evaporator for dirt and any potential clogging. If too much dirt builds up, your AC unit may not turn on at all.
If you have the fan setting on your thermostat set to “on” or “run,” causing it to run all the time, it may just be that the compressor has cycled off and there is nothing wrong. You can also try adjusting the thermostat down and see if the air conditioner kicks on.
The other option is that something is not broken and it needs to be diagnosed to figure out what is causing the problem. An AC unit not producing cool air could be caused by many things, such as: frozen coils, refrigerant, bad compressor, a capacitor that has gone out, etc.