On occasion, a home air conditioning system will fail to come on at the beginning of the season or after a power outage. Before you call a professional, take a few minutes and follow a few simple steps to restart it yourself.
Turn the control on the thermostat to "Off."
Locate the breakers for the air conditioning and heating circuits in the main circuit breaker box. Usually these breakers consist of connecting pairs, since they involve 240 volt circuits.
Pull the heating and air conditioning circuit breakers to the "Off" position. Leave them off for five minutes, and then turn them back to "On."
Adjust the temperature setting on the thermostat to at least four degrees warmer than the room temperature reading.
Turn the system back on by moving the thermostat switch to "Cool."
Move the temperature adjustment on the thermostat to four or more degrees cooler than the room temperature.
Wait three minutes, then place your hand near one of the vents. Hopefully you will feel cool air coming through the vent. If not, call a qualified repairman.