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Is your air conditioner refusing to shut off, even after reaching the set temperature? This can be more than just a minor inconvenience, it’s a sign that something is wrong with your AC system, and it could be costing you money and comfort.

Here’s a comprehensive guide from Orzech Heating & Cooling on how to tackle the issue if your AC is running constantly.

A woman adjusting the thermostat.

Understand the Basics of Your AC System

Before diving into troubleshooting, it’s helpful to understand how your central air conditioner works. An AC unit operates by drawing in warm air from your home, cooling it over the evaporator coils, and then circulating the cool air back into your house. The thermostat plays a crucial role here, as it tells your AC when the desired temperature has been reached.

Common Causes Why Your Air Conditioner Won’t Shut Off

1. Thermostat Problems

The first thing you should check is the thermostat. It could be incorrectly calibrated, which means it’s not accurately reading the indoor temperature. Sometimes, simply recalibrating or replacing the thermostat can resolve the issue.

2. Clogged or Dirty Air Filter

If your air filter is dirty or clogged, your air conditioner has to work harder to circulate air. This not only leads to increased energy consumption but can also cause the unit to run incessantly. Make sure to check and replace your air filter regularly.

3. Frozen Evaporator Coils

Another common issue is frozen evaporator coils. When the coils freeze, they can’t efficiently transfer heat, causing your air conditioner to run continuously. This can be due to low refrigerant levels, poor circulation, dirty coils, power issues at the outdoor unit, setting the AC unit temperature too low at night, or power issues at the condenser.

4. Faulty Compressor

The compressor is the heart of your air conditioning system. If it’s malfunctioning, your air conditioner might not cycle off correctly. Compressor issues are complex and typically require professional attention.

Immediate Steps to Diagnose and Fix the Problem

If you suspect your air conditioner is running non-stop due to any of the issues mentioned above, here are some steps you can take:

1. Clean or Replace Air Filters

A homeowner is replacing the furnace filter.

This is a maintenance task you can easily manage on your own. Dirty air filters restrict airflow, causing your AC to work harder and longer. Regular checks and maintenance of your air filters are essential. Clean or replace them as needed to ensure the efficient operation of your system. This can help prevent your air conditioner from running constantly and increase its efficiency and lifespan.

2. Inspect the Condenser Coil and Lineset

If your air conditioning unit is accessible, take a moment to check the condenser coil and lineset for frost or ice buildup. This indicates a problem with airflow or refrigerant and can prevent your system from cooling effectively. If you notice ice, turn off the unit to let it thaw. Persistent issues with a frozen or dirty condenser coil or lineset should be addressed by a professional, as they can signify deeper problems with your AC system.

3. Consider External Factors

External elements like a heatwave can significantly affect how your AC operates, causing it to run longer than usual. Ensure your home is well insulated and sealed against drafts to maintain cooler indoor temperatures without overworking your AC. Additionally, using window coverings to block out heat during the day can also help keep your indoor environment cooler and reduce the strain on your air conditioning unit.

When to Call a Professional

If you’ve tried the above steps and your AC is still running constantly, it’s time to call a professional. HVAC technicians can diagnose deeper issues that aren’t as straightforward, such as refrigerant leaks or electrical problems. Regular maintenance from a professional can also prevent many of these issues from developing in the first place.

DIY Tips for Preventing AC Overrun

An outside AC unit covered with leaves.

1. Regular Maintenance

Keep your AC unit in top shape with regular maintenance. This includes cleaning the area around the unit, checking for duct air leaks, and ensuring the outdoor unit is clear of debris.

2. Upgrade Your Insulation

Good insulation keeps your home cooler in summer and warmer in winter, reducing the burden on your AC.

3. Use Curtains and Blinds

Sunlight can significantly increase your room temperature. Using curtains or blinds during the hottest parts of the day can keep your rooms cooler.


An AC that runs continuously is a problem that you shouldn’t ignore. Not only does it increase your energy bills, but it also stresses your HVAC system, potentially leading to more significant issues. By understanding common causes and taking proactive steps, you can ensure that your AC runs efficiently and effectively. And remember, when in doubt, calling a professional for an AC repair is always a smart move to keep your system in optimal condition.