Few things are more frustrating than turning on your air conditioner on a hot day, only to find that it’s blowing warm air or barely cooling your home. If your AC unit is running but not doing its job, there could be several reasons why. Some problems are pretty simple to fix, while others may require professional attention. Before calling in an HVAC technician, here are a few common culprits to check.
1. Your Air Filter Is Clogged
The first thing to do is check your air filter. An air filter that is dirty or clogged is one of the most common reasons an AC isn’t cooling properly. When the filter is packed with dust and debris, it restricts airflow, which makes it harder for your system to circulate cool air efficiently.
If your air filter looks dirty, replace it. Most filters should be changed every 1-3 months, especially during the warmer months.
2. The Thermostat Is Set Incorrectly
It may sound obvious, but sometimes the issue is as simple as an incorrect thermostat setting. If your AC is set to “fan” instead of “cool,” it will circulate air without actually cooling it. Double-check that your AC settings are set to “cool” and that the temperature on the thermostat is lower than the current room temperature. If your thermostat is programmable, make sure the scheduling settings are correct.
3. Refrigerant Levels Are Low
Your HVAC system uses refrigerant to cool the air. If the refrigerant levels are low or there’s a leak in the system, it won’t be able to cool properly. Unfortunately, refrigerant issues require a professional HVAC technician. If you notice hissing sounds, ice buildup on the AC coils, or week cooling, it might be time to schedule a service call.
4. The Outdoor Unit Is Dirty or Blocked
Your AC’s outdoor unit needs ample airflow in order to release heat from your home. If it’s covered in dirt, leaves, or other debris, it won’t function effectively. Inspect the outdoor unit for any dirt or blockages, and gently rinse it with a hose if needed. It should have at least two feet of clearance around it.
5. The Evaporator Coils Are Frozen
If your AC is running continuously but not cooling, frozen evaporator coils could be to blame. This can happen due to a dirty filter or low levels of refrigerant. Turn off your AC and let the coils completely thaw. After they have thawed, make sure the filter is clean and airflow isn’t blocked. Call a professional if the issue persists.
6. Your Ductwork Has Leaks
If there are leaks, gaps, or poor insulation in the ducts throughout your home, cool air might be escaping before it reaches your living spaces. If some rooms feel significantly warmer than others, or you notice weak airflow, have your ductwork inspected for leaks or damage. Sealing and insulating ducts can improve efficiency and cooling performance.
When to Call a Professional
While some AC issues can be resolved with simple fixes, others require expert attention. Call an HVAC professional if:
- Your AC runs but never cools below a certain temperature
- You hear unusual noises like hissing, buzzing, or rattling
- You have a sudden, unexplained increase in your energy bill
- There’s ice buildup on your AC components
- The problem persists after fixing the basic problems
If you’re experiencing these problems with your AC, start with simple troubleshooting steps like checking the filter, thermostat settings, and outdoor unit. If the issue is more complex, it’s best to call in a professional. Keeping up with routine AC maintenance can also help prevent many of these problems before they start, helping your home stay cool and comfortable all season long.