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Writer's pictureNatalie Bailey

Top 10 Common AC Problems

Updated: May 22

What are the Most Common AC Problems?


Air conditioning systems are vital for comfort during the hot months, but they can run into issues that affect their performance. Understanding the most common problems can help you identify and possibly troubleshoot issues before they escalate. Here's a rundown of the top 10 AC problems and tips on what you can do about them.



Your AC's evaporator coil, filled with refrigerant, functions like a sponge by absorbing heat from the air. While it may seem counterintuitive, these coils require warm air circulating around them to operate efficiently. When airflow is obstructed, condensation on the evaporator coils can freeze, further restricting airflow and exacerbating the problem.

Common causes of this issue include a dirty air filter or obstructions in the evaporator coil, such as pet hair and dust.


Here's a simple fix you can try:

  1. Replace the Air Filter: A clean air filter ensures proper airflow around the evaporator coil.

  2. Turn Off the AC System: Allow the system to rest for at least 24 hours, giving the evaporator coil time to thaw gradually.


Important Note: Do not turn on the heat to speed up the thawing process. Rapid defrosting can overload the drain system or cause leaks, potentially resulting in water damage.


If issues persist, call Pinnacle Heating and Air Conditioning at 720-338-7037 or Book Online to have a technician come out and look at the issue for you.


2. Dirty Condenser Coils

The coils in your AC's outdoor condensing unit can become dirty due to dust or nearby foliage, particularly cottonwood trees. This dirt buildup leads to poor heat transfer, putting excess stress on vital components and increasing the risk of system failure.


To keep your outdoor unit running smoothly, follow these simple steps:

  1. Clear the Area: Remove any grass, leaves, trees, plants, or weeds growing toward or into the condensing unit.

  2. Regular Maintenance: Periodically check and clean the coils to ensure they remain free of dirt and debris.

By keeping the area around your condensing unit clear and performing regular maintenance, you can help extend the life of your AC system and maintain its efficiency.


Below is an example of a dirty and clean condenser coil.

dirty ac condenser coil and clean ac condenser coil

3. Capacitor Problems

The fan motor and compressor in your AC's outdoor unit rely on a device called a capacitor for proper startup and operation. Over time, capacitors can degrade, leading to weak startups or complete non-operation of the fan motor, compressor, or both.


Signs of a failing capacitor include:

  • A mild humming sound from the condensing unit.

  • No operation from the fan or compressor despite the humming noise.


Estimated Repair Cost: $228 for dual capacitors


4. AIRFLOW Problems

Your HVAC system relies on two critical fans to cool your home effectively.


  1. This motor moves air throughout your house during both heating and cooling operations. Proper airflow is crucial, especially during hot months when your AC is running. An old or inefficient blower motor can cause identical symptoms to a few of the items already discussed such as a dirty filter or evaporator coil.


A few common blower motor issues include:

  • Failed Blower Capacitor: Prevents the blower from starting or running properly.

  • Dirty Blower Wheel: Reduces airflow and efficiency.

  • Broken or Damaged Motor Windings: Leads to motor failure.

  • Bearing/Mechanical Failures: Causes noise and reduced performance.


2. Condensing Fan Motor

The second critical motor in your HVAC system is the condensing fan motor located in the outdoor unit. This motor is responsible for removing heat from the refrigerant during the cooling cycle and keeping the outdoor unit's vital components cool during operation. Much like the blower, it requires proper airflow to function correctly and keep your unit running efficiently.


A few common issues that can affect the condensing fan motor include:

  • Failed Capacitor: Prevents the motor from starting or running properly.

  • Dirty or Clogged Condensing Coils: Reduces airflow and efficiency.

  • Broken or Damaged Motor Windings: Leads to motor failure.

  • Bearing/Mechanical Failures: Causes noise and reduced performance.


5. Contactor OR wiring Problems

The contactor on an air conditioner is a switch that controls the compressor and the condenser fan motor through your thermostat and circuit board. When the contactor fails, the outdoor condensing unit will not run at all.


Sign of a failed contactor:

The outdoor condensing unit is not running, but there is a mild humming or buzzing noise coming from inside the unit.


Estimated Repair Cost: $165


6. Thermostat Problems

Old or inaccurate thermostats can cause your AC to improperly cycle, inefficiently cool, or occasionally not turn on at all.


Upgrading to a newer digital thermostat will help ensure accurate temperature readings, consistent heating and cooling patterns, and allow for convenient scheduling, making it easier to maintain a comfortable home.


7. Clogged Drains

The moisture that your AC system removes from the air has to go somewhere. You'll notice a small drain line (typically made of 3/4" white PVC pipe) on your evaporator coil that directs condensation to the appropriate drainage location. Over time dust, pet hair, and general air debris can accumulate causing clogs and backups.


If the drain line becomes clogged, water can back up and overflow from the drain pan, potentially causing damage to your HVAC system and the surrounding areas.


8. Incorrect Size

If your AC system is too big or too small, it may cycle too frequently or fail to cool your space adequately. An improperly sized unit affects both efficiency and comfort. Ensuring your AC system is correctly sized is essential for optimal performance and maintaining a comfortable home.


9. Refrigerant Leaks OR improper charge

Everything in moderation! Proper refrigerant levels are crucial for your AC system's performance. Both leaks and excess refrigerant can cause significant problems. Low refrigerant, whether from undercharging during installation or a small leak over time, can lead to freeze-ups, inefficient cooling, and potential damage to vital components. Conversely, systems can occasionally be overcharged by mistake resulting in inefficient heat transfer and poor system performance.


It is essential to have a trained HVAC technician repair any leaks, test the system to ensure the repair is effective, then charge the system with the correct amount of refrigerant to ensure your AC system operates efficiently.


10. Leaking Ducts

The ductwork that runs through your walls and ceilings carries the cooled air from the air conditioner throughout your space. However, if there are breaks or leaks in the ducts, that expensive cooled air ends up inside your walls where it’s not doing you any good.


Recognizing these common AC problems can help you address them early before they require expensive repairs. Regular maintenance is the best way to avoid these issues and keep your system running smoothly. Learn more about Pinnacle Heating and Air Conditioning's HVAC Maintenance Services. To Book HVAC Maintenance services such as a Full HVAC System Check or an AC Tune-Up call  or Book Online.


Not sure if your AC is performing at its best? Call 720-338-7037 or Book Online for a comprehensive HVAC system check-up and expert maintenance services to keep your system in prime condition all summer long.

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