When your HVAC system stops working in the middle of a Woodstock summer or a cold January night, it feels like a major catastrophe. However, in our years of serving Cherokee and Cobb County, we’ve found that the vast majority of calls boil down to the same few common HVAC system issues.

Understanding these common problems can help you describe the issue to your technician, or in some cases, resolve it yourself before making a service call.

1. Maintenance-Related Issues

Lack of maintenance is the #1 reason HVAC systems fail prematurely. Neglect leads to strain, and strain leads to broken parts.

  • Clogged Air Filters: A dirty filter is the "silent killer" of HVAC units. It restricts airflow, which causes the indoor coil to freeze in the summer and the furnace to overheat in the winter. Check your filter every 30 days!
  • Dirty Condenser Coils: Your outdoor unit release heat. If it’s covered in dirt, grass clippings, or pollen, it can’t breathe. For a full walkthrough on this, check out our guide on AC condenser coil cleaning.
  • Clogged Condensate Drains: Air conditioners pull humidity out of the air. That water drains away through a small pipe. Algae can grow in that pipe, causing a backup that trips your safety switch and kills your system.

2. Electrical Component Failures

Modern HVAC units rely on precision electrical parts to start and run. These are often the first things to go when the Georgia heat gets intense.

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Blown Capacitors

This is the most common reason an AC won't turn on. The capacitor is like a big battery that gives the compressor the "kick" it needs to start. If it's dead, you'll often hear a humming sound from the outdoor unit but the fan won't spin.

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Bad Transformers

If your thermostat screen is totally blank and your breakers aren't tripped, you may have a bad furnace transformer. This part converts high voltage to the low voltage used by your thermostat.

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3. Mechanical & Refrigerant Problems

Mechanical issues are typically more complex and require an EPA-certified professional to handle safely and legally.

  • Refrigerant Leaks: If your AC is running but blowing warm air, or if you see ice on the lines, you likely have a leak. Refrigerant doesn't "wear out" or "get used up"—if it's low, there's a hole in the system.
  • Failing Furnace Ignitors: In the winter, if the furnace blower is running but the air is cold, the hot surface ignitor has likely cracked. This part is a consumable and typically needs replacement every 5-7 years.
  • Blower Motor Failures: The blower motor pushes air through your ducts. If you hear a loud squealing or scraping sound, the bearings are likely failing, or the motor has burned out due to a clogged filter.

Pro Tip: Before you call for service, always check your thermostat batteries and your electrical panel. Sometimes a simple tripped breaker is the only thing standing between you and a comfortable home!

HVAC Troubleshooting FAQ

Why is my AC running but not cooling?
This is usually caused by restricted airflow (dirty filters), a heavily soiled outdoor condenser coil, or a refrigerant leak. We recommend checking your filter first, then scheduling a professional diagnostic if the issue persists.
Why is my furnace blowing cold air?
A furnace blowing cold air usually has a failed hot surface ignitor or a dirty flame sensor. If the ignitor doesn't glow, the gas won't light, resulting in cold air being circulated by the blower.
How often should I change my HVAC filter?
For standard 1-inch pleated filters, we recommend changing them every 30 to 90 days. If you have pets or allergies, every 30 days is best to prevent system strain.