Why Is My AC Not Cooling? 7 Common Reasons & How to Fix Them
When your air conditioner stops cooling in the middle of a heatwave, it can be frustrating and uncomfortable. Whether your AC is blowing warm air, struggling to maintain the temperature, or not turning on at all, there are several potential causes. In this guide, we’ll explore the seven most common reasons your AC isn’t cooling and what you can do to fix them.
1. Clogged or Dirty Air Filters
A dirty air filter is one of the most common reasons an AC unit struggles to cool a home. Over time, dust, dirt, and debris accumulate in the filter, blocking airflow and reducing efficiency.
Signs of a clogged filter:
Weak airflow from vents
Uneven cooling in different rooms
Increased energy bills
How to fix it:
Check your air filter every 30–60 days and replace it if it looks dirty.
If you have pets or allergies, consider changing it more frequently.
Use high-quality, manufacturer-recommended filters for the best performance.
2. Refrigerant Leaks
Refrigerant is the substance that helps cool the air inside your AC system. If there’s a leak, the unit won’t be able to absorb heat effectively, leading to warm air blowing from your vents.
Signs of a refrigerant leak:
AC is running but not cooling
Hissing or bubbling noises near the indoor unit
Ice buildup on the refrigerant lines
How to fix it:
If you suspect a refrigerant leak, call a professional technician immediately.
Refrigerant handling requires specialized training, so DIY repairs are not recommended.
If leaks occur frequently, it may be time to replace your system.
3. Thermostat Issues
Sometimes, the problem isn’t with the AC unit itself but with the thermostat settings or functionality.
Signs of a thermostat problem:
Incorrect temperature readings
AC won’t turn on or cycles on and off frequently
The system is set to "ON" instead of "AUTO"
How to fix it:
Ensure the thermostat is set to “Cool” and at the correct temperature.
Replace old batteries if it’s a battery-powered thermostat.
Upgrade to a programmable or smart thermostat for better control.
4. Blocked or Dirty Condenser Coils
The outdoor condenser unit is responsible for releasing heat from your home. If the coils are dirty or blocked, heat transfer is restricted, reducing cooling efficiency.
Signs of dirty condenser coils:
AC runs continuously but doesn’t cool effectively
Higher energy bills
Dirt, debris, or grass clippings around the outdoor unit
How to fix it:
Turn off the AC and clean the condenser unit with a garden hose (don’t use high pressure).
Trim back vegetation at least 2 feet around the unit.
Schedule a professional coil cleaning if the buildup is severe.
5. Frozen Evaporator Coil
The evaporator coil absorbs heat from the air inside your home. If it freezes over, airflow is restricted, and your AC will struggle to cool properly.
Signs of a frozen coil:
Ice buildup on refrigerant lines or indoor coils
Weak or no airflow from vents
AC short cycling (turning on and off quickly)
How to fix it:
Turn off the AC to allow the coil to thaw.
Check and replace the air filter.
Ensure vents are open and unobstructed.
If the issue persists, call an HVAC technician to inspect refrigerant levels.
6. Ductwork Leaks or Blockages
Your AC may be working fine, but if there are leaks or blockages in the ductwork, cool air won’t reach certain rooms efficiently.
Signs of duct issues:
Some rooms feel warmer than others
Increased dust buildup in the home
Higher-than-usual energy bills
How to fix it:
Inspect visible ductwork for gaps, tears, or disconnected sections.
Seal small leaks with HVAC tape.
Schedule a professional duct inspection for larger issues.
7. Electrical or Mechanical Failures
Sometimes, an internal component like the compressor, capacitor, or fan motor fails, preventing the AC from working properly.
Signs of electrical/mechanical failure:
AC won’t turn on at all
Clicking or buzzing noises from the unit
Circuit breaker trips frequently
How to fix it:
Check the circuit breaker to see if it has tripped.
Reset the AC system by turning it off for 5 minutes, then back on.
If the issue persists, contact a professional for a full inspection.
When to Call a Professional HVAC Technician
While some AC issues have simple fixes, others require expert repair. Call an HVAC technician if:
Your AC still isn’t cooling after trying these troubleshooting steps.
You suspect a refrigerant leak or electrical issue.
Your unit is more than 10-15 years old and experiencing frequent breakdowns.
Regular AC maintenance can help prevent many of these problems and keep your system running efficiently. If your air conditioner isn’t cooling properly, don’t wait—get it checked before the summer heat intensifies!
