If your air conditioning or heat pump system is not working, performing your own check of the system may enable you to get it running again without having to wait for a service person.

 Ensure the outdoor unit is running.

 Listen for the hum of the compressor and check for an operating fan at the outdoor unit. If not operating, check the circuit breakers in the main circuit breaker panel or at the service disconnect near the unit (most likely mounted to an outside wall). Is it in the "On" position? If it “Off” and wasn’t deliberately turned off by someone (such as one might do if going on an extended vacation), it is best to leave it off and call for service. The breaker may have tripped due to an electric short or overload problem.

Ensure that the blower in the furnace cabinet or air handler is running.

 If the thermostat is in the "COOL" position and the room temperature is above the setpoint, the blower should be running. If not, check to make sure the switch at the furnace or air handler is in the "ON" position

Check the filter condition.

 An extremely dirty or blocked filter can cause your air conditioner to shut down due to lack of proper airflow. Your filter should be checked and, if needed, changed every month. Typically the filter is located at the air handler; however, it may also be found at a central return air grille (more common for ceiling returns with packaged units in attics).

Check all return air grilles to make sure they are not blocked by furniture or other items.

 Check all supply air registers to make sure they are open and blowing air. Air should be drawn into the return air grilles at a steady rate. Returns are normally the larger grilles located on interior walls, or the ceiling.

Check the condensate system.

 Some air conditioning and heat pumps systems have a device installed in the condensate pan or at a condensate pump to shut down the system to prevent an overflow when lines become blocked. Check to make sure all pans and drains are free flowing and terminated properly.

 If addressing these issues doesn’t get the unit running again, then it’s time to call a qualified HVAC service company.