If you are having troubles with your air conditioner, before calling a contractor follow these steps to troubleshoot why your AC may not be running as expected. , or you can also check the lights on your radio receiver (located on your home). Was the AC unit on/running prior to controlling?
If yes, and we are controlling, then it's most likely in the middle of the control cycle so your AC unit won't run again until the cycle is over. Remember, during control periods your AC will cycle on and off. Cycle time will vary depending on your AC unit and the radio installed. Is the thermostat set to cool?
If not, you'll need to set it to cooling mode. Please note: If you are turning your AC unit on in the middle of a control period, your AC unit may not come on right away. It could take up to 30 minutes for it to cycle back on. We recommend turning your AC unit on in advance of hot weather to ensure the home is pre-cooled. Is the temperature on the thermostat set lower than the temperature in the house?
If no, set the temperature lower and listen for the AC unit to turn on.

We recommend turning your AC unit on in advance of hot weather to ensure the home is pre-cooled. 

If you have a programmable thermostat and are not able to see a display of the temperature, the thermostat has likely lost power or is disconnected somewhere. Call a contractor for help. Is the air conditioning circuit breaker turned on?
If yes, turn the breaker off, then on and wait 15-20 minutes for the radio to reset. Only do this once. Is the AC disconnect box (located outside by AC unit) circuit breaker in the ON position?
If not, pull out the handle and turn it to the position that says "ON". Be sure to push the handle back in. Are there any fuses in your air conditioners disconnect box?
If yes, are they good? Most hardware stores carry disconnect fuses and can test them. Is the furnace fan blowing air?
If not, that means a fuse or something in the furnace is disconnected and a contractor is needed for more trouble shooting.
If it is and your AC still does not turn on, call a contractor for help trouble shooting.