Managing Your HVAC System

How to Fix Central Air Unit Short Cycling

If you notice your central air shuts off before it reaches the pre-set temperature, the unit is short cycling. Short cycling occurs when the unit shuts on and off constantly, typically in under twenty minutes, which is the normal length. 

Short cycling can cause extra wear and tear on the unit, and it should be addressed as soon as possible. You should be able to troubleshoot short cycling by following these troubleshooting steps.

Clean the Filters

Not cleaning the air filters can cause buildup, which forces the unit to work harder. Air filters are commonly located behind the air grille inside the home.

Shut off the power to the unit or unplug it. Use a screwdriver to detach the screws on the grille, set parts aside, and pull the filters out by hand.  

Soak removable filters in several drops of dish soap and warm water, rinse, then let them dry. Clean non-removable filters with a dampened soft brush, and replace damaged filters.

Relocate the Thermostat

Inspect the location of the thermostat. Thermostats placed near return air vents or a window could misread the temperature from blasts of cold or hot air. The air surrounding the thermostat should be the same as the rest of the area. 

Move the thermostat, or hire a professional to rewire it for you. Inspect the wiring while you have it down to ensure it is firmly secured and not damaged. Replace thermostats that have damaged wiring.

Check Refrigerant, Condensate Drains, and Evaporator Coils

The refrigerant is the liquid that helps to cool down the air as it passes over coils. Low refrigerant levels or leakage interfere with the compressor's ability to fully operate, and it stresses other components.

Signs of leaks or low levels include blowing hot air and frozen refrigerant lines. Only certified HVAC technicians should handle replacing refrigerant. 

Frost building up on coils can also lead to short cycling. Turn off the unit for two hours, and see if it melts the ice.  

Clogged condensate drains on central air units can cause short cycling. Locate the drain, which is commonly a small line on the outside unit with water dripping from it. Turn off the unit, wear gloves, soak water with a rag, then try to remove the clog with a shop vac.

Install a Smaller Unit

Bigger air conditioners don't mean efficient. Air conditioners that are too large cause constant cycling, which runs up energy bills. The extra strain on the unit wears out parts, which reduces its life span. 

Your home may feel hotter, and the indoor air quality is reduced since the unit can't stay on long enough to filter air. Get the load capacity calculated for your home to determine the correct unit size.

​When in doubt, contact an HVAC contractor who offers air conditioner services to help you troubleshoot the short cycling issue.