5 Things to Check When Your Air Conditioner Doesn’t Come On

Here are five things a homeowner can check before calling a professional cooling company.

1. Is the thermostat set correctly? This means that the function switch is showing cool and the set point temperature (the desired temperature) is at least two degrees below the actual temperature in the home. Some setback or programmable thermostats can be confusing. If you are in the programming mode and switch the function to cool, the system may not come on. You must be out of the programming mode for the thermostat to activate the cooling system.
2. Wait at least 5 minutes after turning the system to cool for the air conditioner to energize. Many thermostats have a built in time delay and some air conditioners also have a time delay. This prevents the system from quick cycling which could damage the compressor.
3. Turn the fan on at the thermostat. You should now have air circulation in the home. If nothing happens with the fan in the on position, then check the power to the furnace. If there is power to the furnace the fan motor may be faulty or the circuit board in the furnace is faulty.
4. Does the air conditioner fan operate in the outside unit? If it is on, then there is power to the outside unit. If it is not on, then there may not be power to the outside unit. Check the breaker box and make sure the double pole air conditioner breaker is on. If there is a humming in the outside unit but the fan is not operating then turn the power off to the unit. Check for obstructions like a tree branch that may be impeding the fan from turning.
5. If your indoor fan is running and the outside unit fan is running but the air coming out of the registers is not cool, the compressor in the outside unit may not be operating. You can touch the larger of the two copper pipes coming out of the unit and see if it is cold.

If it cold then the compressor is running. If it is not then the compressor is either not running or has an incorrect refrigerant charge.
At this point it is best to call a professional cooling company.
Having a dirty furnace filter or a dirty outside unit coil will not prevent the system from cooling for a while. Both of these items a homeowner can do themselves. Keep a clean air filter in the system and keep the outside coil clean by washing it down with water from a hose. The back side of the air conditioner (closest to the house) which the rain does not hit will be the dirtiest. Always check this side and keep the entire coil clean so your utility bills will be the lowest possible.