Why Is My Air Conditioner Running but Not Cooling the House?

Brian Rogers

Feb 02 2026 18:28

If your AC is running but your home still feels warm, the most common causes are a dirty air filter, blocked outdoor unit, thermostat issues, or low refrigerant. Start by checking your thermostat and replacing the air filter—these quick fixes solve many cooling problems. If the system still won’t cool, it’s time to bring in a professional. Climate Wise HVAC, the leading air conditioning repair company in Christiansburg and the New River Valley, can diagnose the issue quickly and get your home comfortable again.

Step 1: Check the Thermostat Settings

This may sound simple, but thermostat errors are one of the most common reasons an AC runs without cooling.

  • Make sure it’s set to Cool and not just Fan.
  • Set the temperature at least 3–5 degrees below your current indoor temperature.
  • Replace batteries if your thermostat has them.

If the thermostat is malfunctioning or losing communication with your system, the AC may run but never drop the temperature.

Step 2: Replace or Clean the Air Filter

A clogged filter restricts airflow so severely that cool air can’t circulate through your home.

  • Check the filter and replace it if it’s dirty—most should be changed every 1–3 months.
  • If you have pets or allergies, you may need to replace it more frequently.

This is one of the easiest DIY fixes and often restores cooling immediately.

Step 3: Inspect the Outdoor Unit

Your outdoor condenser coil needs plenty of airflow to release heat. If it’s blocked or covered in debris, the system can’t cool effectively.

  • Remove grass, leaves, or debris around the unit.
  • Ensure the unit has at least 2–3 feet of clearance on all sides.
  • If the coil is visibly dirty, it may need professional cleaning.

Step 4: Check for Frozen Evaporator Coils

If the indoor evaporator coil freezes, your AC may blow warm or barely cool air.

  • Turn the system off for several hours to let it thaw.
  • Check the filter and airflow once thawed.

A frozen coil usually points to low refrigerant, restricted airflow, or mechanical issues.

Step 5: Consider a Possible Refrigerant Leak

An AC that runs constantly but never fully cools often has low refrigerant due to a leak. This is not a DIY fix.

Signs include:

  • Ice on refrigerant lines
  • Hissing or bubbling noise
  • Warm or weak airflow from vents

Only a licensed HVAC technician can diagnose and repair refrigerant issues.

Step 6: Inspect Ductwork (If Accessible)

Leaks or disconnected ducts can let cool air escape into attics or crawlspaces instead of reaching your living areas. If you notice weak airflow in certain rooms, this could be the cause.

When to Try a DIY Fix—and When to Call a Professional

DIY Fixes You Can Try Safely

  • Replace the air filter
  • Check thermostat settings
  • Clear debris from the outdoor unit
  • Reset breakers to ensure the system has power

Call a Pro If You Notice Any of These

  • Frozen evaporator coil
  • Hissing sounds or suspected refrigerant leak
  • Water around the indoor unit
  • Burning smells or electrical issues
  • System is running non-stop without cooling

Climate Wise HVAC provides fast, reliable diagnostics and repairs for homeowners across Christiansburg and the New River Valley. Explore our full AC repair and maintenance options here: Air Conditioning Services.

Need AC Help Fast? We’ve Got You Covered.

If your air conditioner is running but not cooling, our experienced technicians can pinpoint the problem and restore comfort quickly. Don’t wait—issues like refrigerant leaks or airflow restrictions can get worse over time. Contact Climate Wise HVAC today to schedule prompt, professional service: Get in Touch. Our team is here to help you stay cool, comfortable, and confident in your home’s HVAC system.