Central air unit works but does not cool

Central air conditioning units are often used to cool a home or business during periods of hot and humid weather. A central unit pushes the hot air into the machine, cools the air, and sends it through the home or business through the air duct system. If the central air conditioning unit is working but not cooling, there are a variety of possible reasons why this can happen, some of which are easily solved and some of requiring professional help.

Central air unit works but does not cool

Thermostat setting

If the thermostat for the air conditioner is set to a temperature that is higher than the actual temperature, the air conditioner will have power but will not cool, which is not a defect or a problem and can be easily solved by setting the thermostat selector to “Cool” and selecting a temperature approximately 10 degrees lower than the current air temperature. If the thermostat is battery powered, make sure the batteries are charged.

High-pressure switch

If the fan turns on and blows after the thermostat has been set to a cold temperature, but the central unit does not turn on or start blowing cold air, look for a button that is sticking out of the side of the case, which is a high-pressure switch that may have tripped. It can be reactivated by pressing the button again on the cabinet. When investigating the central unit, check that the main power is “On” and the indoor power switch is turned on as well.


The air conditioner may simply need to be cleaned to resume proper operation. Disconnect the power supply to the air conditioner first, and then clean and remove any leaves, flowers, grass, or debris that may be blocking the vents and vents on the central unit. Remove objects that may block the flow of air to and from the air conditioner. Remove the top and side vents from the air conditioner and use a soft brush to gently clean the condenser fins. Suck up any dirt with a cleaning vacuum brush. Close the side and top vents firmly before restoring power. Look at return air registers throughout the home or business and remove furniture, curtains, or anything else that could block airflow through the registers.

Air filter

If the air conditioner air filter is dirty or clogged with lint and other debris, the unit will not cool normally. Disconnect power to the unit and remove the air filter from the main access panel. If the air filter is a permanent filter, it can be vacuumed or washed with warm soapy water. Rinse the filter and let it dry before putting it back in the unit. If the air filter is a disposable filter, replace it with a new filter.

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