How to Troubleshoot Common AC Problems
July 21, 2025
Is your AC unit not cooling properly? Before you panic, there are a few common issues that you can check yourself. In this guide, we'll go over the following AC troubleshooting steps:
- Check the thermostat and power supply
- Inspect airflow and replace dirty filters
- Look for frozen coils or refrigerant issues
- Listen for strange noises or vibrations
- Know when to call a professional
By the end of this article, you'll have a better idea of what's wrong and whether you need to call a professional.
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Check the Thermostat and Power Supply
When troubleshooting AC problems, start with the thermostat. Your AC follows instructions from the thermostat; so, if the settings are incorrect, the air conditioner won't work properly. Here are some quick things to check:
- Thermostat mode. Make sure the thermostat is set to "cool" (not "heat") and its temperature is lower than the room's temperature.
- Fan mode.The fan should be set to "auto," not "on."
- Display. A blank display means you may need to replace the batteries.
In addition to assessing the thermostat, check the power supply and breaker panel. A malfunctioning AC is often caused by a power issue or faulty wiring.
Inspect Airflow and Replace Dirty Filters
Is your airflow weak or nonexistent? You may have clogged filters. Over time, contaminants can block your HVAC filters, preventing the system from releasing cool air. In more serious cases, it can make your system overheat and shut down. You can improve airflow with the following tips:
- Replace filters monthly. You should replace your filters every 30 days, especially during the summer.
- Clear debris. Remove any debris (such as leaves or dirt) from the outdoor unit.
- Check the vents. Make sure all your HVAC vents are open and not blocked by furniture.
Along with restoring comfort, improving airflow helps protect your HVAC system from further damage.
Look for Frozen Coils or Refrigerant Issues
If your AC system is running but not cooling, the problem may lie with the evaporator coil or refrigerant levels—both of which are integral to the cooling process. The coil contains refrigerant that absorbs heat from your home. Poor airflow can freeze the coils and lower refrigerant levels, reducing cooling.
Ice buildup on the indoor coil or refrigerant lines is the most common sign of freezing. To fix this, turn off the AC and let it thaw. If the problem isn't resolved, you might have a refrigerant leak requiring expert assistance. It's important not to ignore this problem, as doing so can cause a full system breakdown.
Listen for Strange Noises or Vibrations
One of the most common signs of AC problems is strange noises. Here are some common noises and what they indicate:
- Banging. Banging or clanking suggests you have loose, broken components.
- Hissing. Hissing sounds are signs of refrigerant leaks.
- Buzzing. Buzzing noises can be caused by electrical issues or a faulty capacitor.
- Grinding. Grinding sounds are often caused by a worn-out motor.
The sooner you address strange noises, the sooner you can fix your AC and help prevent costly repairs.
Know When to Call a Professional
While some AC problems are easy to fix on your own, others require expert attention. You should call a professional if you meet any of the following conditions:
- Troubleshooting your AC system doesn't work. Get a professional diagnosis if your AC unit still won't produce cool air after basic troubleshooting.
- There are signs of major problems. Certain AC problems, such as refrigerant leaks, broken motors, and electrical issues, aren't safe to handle on your own. If you suspect any of these issues, contact a professional immediately.
- You have unexpected energy costs. Many AC problems strain your system, reducing energy efficiency and increasing monthly costs. If your bills go up unexpectedly, you may be unaware of a hidden problem.
One of the best ways to prevent problems from occurring is through annual maintenance. At Advanced Air, we offer a comprehensive maintenance plan that identifies problems early and keeps your system running smoothly.
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- Air Conditioning