Why is My AC Running But Not Cooling?

As the summer heat sets in, a malfunctioning air conditioner can be a source of frustration. If you’re experiencing the problem of your AC running but not cooling your space, there are several potential causes to investigate. In this section, we will explore troubleshooting steps to help you identify and fix the issue.

Key Takeaways:

  • The AC not cooling issue is a common problem during summer.
  • Several factors, including thermostat settings, dirty air filters, low refrigerant levels, condenser unit issues, and faulty ductwork, can cause AC cooling issues.
  • To fix the issue, you need to identify the specific problem and take appropriate troubleshooting steps, like adjusting thermostat settings, cleaning air filters or seeking professional assistance.

Thermostat Settings

If your AC is running but not cooling, the first thing to check is your thermostat settings. Incorrect temperature settings or a malfunctioning thermostat can prevent your AC from providing cool air.

To ensure your thermostat is set correctly and functioning properly:

  1. Check the temperature setting: Verify that the temperature setting on your thermostat is lower than the current temperature in your space. Setting the thermostat too high can cause your AC to run but not cool.
  2. Change the temperature setting: If the temperature setting is correct, try adjusting it by a few degrees to see if it makes a difference in the cooling process.
  3. Replace the batteries: If your thermostat runs on batteries, low battery levels can cause it to malfunction. Replace the batteries, even if they do not seem low, to see if it resolves the problem.
  4. Call a professional: If your troubleshooting efforts do not resolve the issue, it may be time to call a professional to inspect and repair your thermostat.

Properly functioning thermostat settings are crucial to ensuring your AC cools your space effectively. Take the time to check and adjust your thermostat settings, and you may be able to solve the cooling problem without calling in a professional.

Air Filter Maintenance

When your AC is running but not cooling, a dirty or clogged air filter might be the culprit. A dirty filter can obstruct airflow and reduce the amount of cool air your AC can produce. To ensure your filter is not causing the issue:

  1. Turn off the power to your AC system.
  2. Find the air filter. It is usually located near the air handler or in the return air duct.
  3. Remove the filter, and inspect it.
  4. If it is covered in dirt and debris, replace it with a new one. If it looks clean, place it back into the unit.

If your filter is dirty, you should clean or replace it every two to three months. The frequency may vary depending on usage and the type of filter. A clogged filter can reduce AC airflow, causing your system to work harder and use more energy, which can result in higher utility bills.

If cleaning or changing the air filter does not resolve the issue, then the problem might lie elsewhere. Check the other troubleshooting steps to identify and fix the problem.

Refrigerant Levels

If your AC is running but not cooling, low refrigerant levels could be the culprit. Refrigerant is responsible for absorbing heat from the indoor air and transferring it outside. If the refrigerant levels are low, the AC won’t be able to cool the air effectively, resulting in warm air being blown from the unit.

Low refrigerant can be caused by a leak in the system, so it’s essential to check for any signs of leakage. A refrigerant leak is a serious issue that requires professional attention. If you suspect a leak, turn off your AC and call a licensed technician immediately.

To check the refrigerant levels, you will need a set of gauges. Connect the gauges to the service valves on the refrigerant lines and turn on the AC. The gauges will display the current refrigerant levels. If the levels are low, add refrigerant until they reach the manufacturer’s specifications.

Remember that adding refrigerant is not a DIY task and should only be performed by a licensed technician. Overcharging the system with refrigerant can be just as harmful as having low levels.

Condenser Unit Issues

When your AC is running but not cooling, the problem may lie with your condenser unit. This outdoor unit is responsible for transferring heat from inside your home to the outside, allowing cooler air to circulate inside. A malfunctioning condenser unit can prevent this process from happening, resulting in warm air blowing from your vents.

One of the most common issues with condenser units is a malfunctioning fan. The fan is responsible for drawing air into the unit to cool the refrigerant. If the fan is not working correctly, the refrigerant cannot cool down, and the AC will blow warm air. Check to see if the fan is spinning correctly and inspect it for any damage or debris that may be obstructing its movement.

The compressor, another crucial component of the condenser unit, can also cause cooling issues when not functioning correctly. The compressor is responsible for compressing the refrigerant to facilitate the cooling process. If the compressor is not working correctly, the refrigerant cannot cool, and the AC will blow warm air. Listen for any unusual sounds coming from the condenser unit and inspect the compressor for any visible damage.

If you suspect that your condenser unit is causing the cooling issue, it’s essential to address the problem promptly. A malfunctioning condenser unit can cause other components of your AC system to work harder than necessary, potentially leading to further damage and even system failure. Contact a professional HVAC technician to diagnose and repair any condenser unit issues.

Ductwork Problems

If your air conditioner is running but not cooling your space, faulty ductwork could be the culprit. Ductwork is the system of pipes that carries conditioned air from your AC unit to different rooms in your home. Problems with your ductwork can result in improper airflow and inadequate cooling.

One common issue with ductwork is duct leaks. If there are leaks in your ducts, cool air can escape before reaching its intended destination. This can result in rooms not being cooled adequately, even if your AC unit is working properly. To check for duct leaks, inspect your ducts for any visible signs of damage or disconnection. You can also hire a professional to conduct a pressure test to identify leaks.

Another problem with ductwork is improper insulation. Insufficient insulation can cause cool air to warm up before it reaches its destination. This can result in rooms not being cooled enough, even if your AC unit is functioning correctly. To address this issue, ensure that your ducts are properly insulated and that any damaged insulation is replaced.

To test if your ductwork is the issue, try the following:

  1. Close all windows and doors in your home.
  2. Turn on your AC unit and let it run for a while.
  3. Inspect the air coming out of your vents. Check if the air feels weak or if it’s not reaching some rooms.
  4. If you notice weak airflow or insufficient cooling in specific rooms, inspect the ducts leading to those rooms.
  5. If you find any leaks or insulation issues, address them accordingly.

Fixing ductwork problems can be complex and require professional assistance. If you’re unsure of what to do or need help with your ductwork, don’t hesitate to contact a qualified HVAC technician.


As we’ve discussed, several potential issues could cause your AC to run but not cool your space effectively. By following the troubleshooting steps outlined in this article, you can identify and fix many of these problems on your own.

Start by checking your thermostat settings and ensuring they match your desired cooling level. If necessary, adjust the settings or replace the thermostat entirely.

Then, move on to the air filter. A dirty or clogged filter can restrict airflow and hinder the cooling process. Check the filter and either clean or replace it as needed.

If neither of these steps resolves the issue, move on to checking your refrigerant levels. Low refrigerant levels or a refrigerant leak may require professional attention and should not be attempted as a DIY fix.

Next, inspect the condenser unit for any issues, such as a malfunctioning fan or compressor. If you notice any problems, try the steps we outlined in Section 5.

Finally, take a look at your ductwork. Problems with duct leakage or improper insulation may hinder airflow and prevent your AC from cooling efficiently. Fix any issues you find to improve overall performance.

We hope this article has provided you with valuable insights and troubleshooting tips to fix AC cooling problems. Remember, if you’re unable to address the issue on your own, it’s always best to seek professional help for your AC needs.


Why is my AC running but not cooling?

There are several potential reasons for this issue. It could be due to incorrect thermostat settings, a dirty or clogged air filter, low refrigerant levels, problems with the condenser unit, or faulty ductwork. By troubleshooting these areas, you can identify and fix the problem.

How do I check and adjust my thermostat settings?

Start by ensuring that your thermostat is set to the desired cooling temperature. Make sure it is set to “cool” mode and not “fan” or “heat.” If the desired temperature is lower than the current room temperature, the AC should kick in. If not, consider checking the batteries in your thermostat or consult the manufacturer’s instructions for further troubleshooting.

What should I do if my air filter is dirty or clogged?

Begin by locating the air filter, typically found near the air handler or furnace. Remove the filter and inspect it for dirt or debris. If dirty, either clean the filter if it is reusable or replace it with a new one. Regularly cleaning or replacing your air filter every 1-3 months can help maintain proper airflow and improve cooling efficiency.

How can I check my AC’s refrigerant levels?

Checking refrigerant levels requires specialized equipment and is best left to a professional HVAC technician. If you suspect low refrigerant levels, contact a licensed technician who can evaluate your system, identify any leaks, and recharge the refrigerant if necessary.

What might be causing issues with my condenser unit?

Problems with the condenser unit, such as a malfunctioning fan or compressor, can prevent your AC from cooling. Ensure that the outdoor unit is free of debris or obstructions and that the fan is spinning properly. If the fan or compressor is not working, contact a professional technician to diagnose and repair the issue.

How can I identify and fix ductwork problems?

Inspect your ductwork for visible leaks, gaps, or disconnected sections. Seal any leaks with duct tape or mastic sealant and ensure that all connections are secure. Additionally, properly insulate your ducts to prevent heat transfer and improve airflow. If you are unsure or unable to address the issues yourself, consider contacting a professional HVAC technician for assistance.

Simply call or email us to request a quote for your HVAC installation needs, and we’ll be happy to discuss your options and provide a competitive price.

Our address is 7931 E Pecos Rd Mesa, AZ 85212 or call 480-903-8431 today.

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