A broken thermostat generally does not mean the air conditioner is broke as well. If the thermostat does not turn on, first and for most thing to do would be check the electrical outlet to the house/business. You might surpirse to know the number of times people ignore to check their breaker box before calling a hvac technician. Once you check the breaker box, I would recommend removing the cover of the therostat and cleaning the bimetallic coil, as well as the switch contact surface, in case the thermostat does not have mercury switch. Check if the terminals are not loose and also make sure that the thermostat is aligned properly. Once you do so, and the thermostat still does not turn on, its time to call a hvac professional.