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Few things are more frustrating than an air conditioner that runs constantly but does not cool your home especially during a sweltering South Carolina summer. You hear the fan humming, feel air coming from the vents, but the temperature inside just keeps climbing.
At Waldrop Plumbing Air Electric, we have diagnosed and repaired thousands of AC systems across Greenville, Spartanburg, Anderson, Duncan, and Greer over the past 50+ years. Our NATE and NCI-certified technicians know exactly what causes this issue and how to fix it fast.
In this guide, we will walk you through the seven most common reasons your AC is running but not cooling, what you can check yourself, and when it is time to call a professional.
7 Reasons Your AC Is Running But Not Cooling
1. Dirty or Clogged Air Filter
This is the #1 culprit and the easiest fix. A clogged air filter restricts airflow, forcing your system to work harder while delivering less cool air. In extreme cases, it can cause your evaporator coil to freeze, completely blocking airflow.
What to do: Check your filter every 30 days during cooling season. If it is gray, dusty, or caked with debris, replace it. We recommend MERV 8-11 filters for most homes in Upstate SC.
2. Frozen Evaporator Coil
When airflow is restricted or refrigerant levels are low, the evaporator coil can freeze over. You might notice ice buildup on the indoor unit or refrigerant lines. A frozen coil cannot absorb heat, so your AC blows warm air.
What to do: Turn off your AC and let the coil thaw (2-4 hours). Check your air filter and ensure all vents are open. If the coil refreezes, you likely have a refrigerant leak or airflow issue. Call Waldrop for diagnosis and repair.
3. Low Refrigerant (Freon Leak)
Refrigerant is the lifeblood of your AC system. It absorbs heat from your home and releases it outside. If you have a leak, refrigerant levels drop, and your system cannot cool effectively. Signs include hissing sounds, ice on the lines, and longer cooling cycles.
What to do: Refrigerant leaks require an experienced HVAC technician. Never attempt a DIY recharge. It is dangerous, illegal without EPA certification, and will not fix the underlying leak. Our team will locate the leak, repair it, and recharge your system to factory specs.
4. Dirty Condenser Coils
Your outdoor condenser unit releases the heat your AC pulls from inside. When the coils get coated in dirt, pollen, grass clippings, or cottonwood fluff (common in Greenville), heat cannot escape efficiently. Your system runs longer but cannot reach your thermostat setting.
What to do: Turn off power to the unit. Gently spray the coils with a garden hose (not a pressure washer). Trim back vegetation within 2 feet of the unit. For stubborn buildup, schedule professional coil cleaning.
5. Faulty Thermostat
If your thermostat is miscalibrated, placed in direct sunlight, or has dying batteries, it may not signal your AC to cool properly. You might also have it set to Fan Only instead of Auto or Cool.
What to do: Check your thermostat settings. Make sure it is on Cool and set 3-5°F below room temperature. Replace batteries if needed. If the problem persists, you may need thermostat recalibration or replacement.
6. Malfunctioning Compressor or Capacitor
The compressor is the heart of your AC. It pressurizes refrigerant and pumps it through the system. If the compressor or its capacitor (the part that starts it) fails, your outdoor unit may hum or click but will not cool. This is a serious issue.
What to do: Turn off your AC immediately. Continuing to run a failing compressor can cause expensive damage. Call Waldrop for emergency diagnostics and repair. Compressor replacement is a major repair, and we will help you weigh repair vs. replacement options.
7. Undersized or Aging AC Unit
If your AC has always struggled to keep up or if you have added square footage, insulation issues, or more heat-generating appliances, your system may simply be too small or too old. AC units lose efficiency over time, especially if they are 12+ years old.
What to do: Schedule a load calculation with Waldrop. We will assess your home cooling needs and recommend the right-sized system. Upgrading to a high-efficiency model can cut your energy bills by 20-40%.
When to Call a Professional HVAC Technician
Some AC issues are DIY-friendly (like changing a filter), but most require specialized tools, refrigerant handling licenses, and system diagnostics that only a trained technician can provide.
Call Waldrop Plumbing Air Electric if:
• Your AC is blowing warm air after you have replaced the filter
• You see ice on the indoor coil or refrigerant lines
• The outdoor unit is not running or makes grinding/clicking noises
• Your energy bills have spiked without explanation
• The system is 10+ years old and requires frequent repairs
With 50+ years of experience, 7,800+ five-star reviews, and a BBB A+ rating, Waldrop’s experienced technicians deliver fast, reliable AC repairs across Greenville, Spartanburg, Anderson, Duncan, and Greer.
How to Prevent AC Cooling Problems
Most AC failures are preventable with regular maintenance. Here is what we recommend for every homeowner in Upstate SC:
• Replace air filters every 30-60 days during summer
• Schedule annual AC tune-ups before cooling season
• Keep outdoor unit clear of debris and vegetation
• Upgrade to a programmable or smart thermostat
• Join Club Wally for priority service, annual maintenance, and discounts
Club Wally members enjoy peace of mind with annual inspections, priority scheduling, and exclusive discounts on repairs and replacements. It is the smartest way to protect your investment and avoid emergency breakdowns.
Frequently Asked Questions
Why is my AC blowing warm air instead of cold?
Warm air usually means low refrigerant, a frozen evaporator coil, dirty condenser coils, or a failing compressor. Start by checking your air filter and thermostat settings. If the problem persists, call Waldrop for diagnostics.
How long should it take for my AC to cool my house?
A properly sized, well-maintained AC should cool your home by 1°F every 15-20 minutes. If it takes hours or never reaches your set temperature, you likely have an airflow, refrigerant, or sizing issue.
Can I run my AC if it is not cooling?
No. Continuing to run a malfunctioning AC can cause further damage (like compressor burnout) and higher repair bills. Turn it off and schedule service as soon as possible.
How much does AC repair cost in South Carolina?
Minor repairs (like capacitor or contactor replacement) typically cost $150-$1000. Major repairs (compressor replacement, refrigerant leak repair) can run $800-$4,500. At Waldrop, we provide upfront pricing before we start any work.
Should I repair or replace my AC?
If your system is under 10 years old and the repair is less than 50% the cost of a new unit, repair makes sense. If it is 12+ years old, uses R-22 refrigerant, or requires frequent fixes, replacement is usually smarter.
Get Your AC Cooling Again, Fast
An AC that runs but does not cool is more than an inconvenience. It is a sign of a deeper issue that will only get worse (and more expensive) if ignored. Whether it is a simple filter swap or a major compressor repair, Waldrop Plumbing Air Electric has the experience, training, and tools to diagnose and fix it right.
Call us today at (864) 536-0887 or visit www.callwaldrop.com to schedule same-day AC repair in Greenville, Spartanburg, Anderson, Duncan, or Greer.
