Why Is My Air Conditioner Running Outside but Not Inside?

Air conditioning plays a critical role in providing comfort inside our homes, particularly during the sweltering summer months. One common issue homeowners face is the air conditioner unit running outside, but not inside. This situation can leave you puzzled and sweating, questioning what could be going wrong.

The core of this issue lies within the split system of your air conditioner. The outdoor unit may be functioning correctly, but if the indoor unit isn’t working, it won’t circulate cool air throughout your house. Hence, your air conditioner seems to be running outside, but not inside.

This odd behavior of your air conditioner may signal a few specific problems, including a faulty thermostat, power supply issues, ductwork problems, or even frozen evaporator coils. But worry not, each of these can be addressed effectively to restore your indoor comfort.

Causes of the Issue

Air conditioning units are complex systems that could face a number of issues due to various reasons. While it’s daunting when the air conditioner is running outside but not inside, this situation often narrows down to a few key causes. Understanding these causes can give us the foundation needed to address the issue.

Faulty Thermostat

The thermostat is a critical component that controls your air conditioner’s operations. It regulates the temperature by communicating with both your indoor and outdoor units.

  • If your thermostat isn’t functioning as expected, it might fail to signal the indoor unit to start operation, although the outdoor unit might be running.
  • The problem could be due to old age, electrical issues, or incorrect settings.
  • The display may not light up, or it might show incorrect temperature readings, indicating a problem with the thermostat.
Why Is My Air Conditioner Running Outside but Not Inside

Power Supply Concerns

Electricity is what powers your air conditioner. Your indoor and outdoor units are typically connected to different electrical circuits.

  • If the circuit breaker connected to the indoor unit trips, it might cut off the power supply to the indoor unit, but the outdoor unit could still continue to run if it’s on a different circuit.
  • The trip could be due to an overload, short circuit, or ground fault.
  • If only certain parts of your house have power while others don’t, you might be dealing with a partial power outage.

Ductwork Problems

Ductwork serves as the pathway for cooled air from your air conditioner to reach different parts of your home.

  • If there are problems with the ductwork, such as blockages or leaks, the flow of cool air can be affected.
  • Accumulation of dust, debris, or mold can cause blockages.
  • Leaks can occur due to the ductwork’s age, poor installation, or physical damage.

Frozen Evaporator Coils

The evaporator coil is an essential part of your air conditioner located inside the indoor unit. It absorbs heat from the air in your home, creating the cool air that is then circulated.

  • If the evaporator coil becomes frozen, it cannot absorb heat effectively, resulting in a decrease or complete stop in cool air production.
  • Causes of a frozen coil can include a dirty air filter blocking the airflow to the coil, low refrigerant levels, or issues with the fan that circulates air over the coil.
Why Is My Air Conditioner Running Outside but Not Inside

Common Fixes

Addressing the issue of your air conditioner running outside but not inside requires diagnosing the underlying problem accurately. Once you have identified potential causes, you can take appropriate measures. Here are some common fixes for the issues identified.

Checking and Resetting the Thermostat

  • Ensure that the thermostat is set correctly to the “cool” mode and the desired temperature.
  • Replace the batteries if the display is not lighting up, as weak or dead batteries could affect its functioning.
  • Reset the thermostat according to the manufacturer’s instructions if you suspect a programming issue.

Restoring Power Supply

  • Inspect your electrical panel to check if the circuit breaker for the indoor unit has tripped. If it has, switch it back on.
  • If the breaker trips again, it indicates an underlying electrical issue which should be addressed by a professional.
  • For a partial power outage, you might need to contact your power company.

Fixing Ductwork

  • Regularly change or clean your air filters to prevent dust and debris accumulation that can lead to ductwork blockage.
  • Inspect your ductwork for leaks or damage, especially in accessible areas. A professional should handle a comprehensive inspection and any necessary repairs.

Thawing Frozen Coils

  • Change or clean your air filter if it is dirty, to restore airflow to the coil.
  • If you suspect low refrigerant levels, contact a professional to inspect and recharge your system.
  • Give your system a break and allow the ice to thaw if the coils are frozen.

When to Call a Professional

While some issues can be handled independently, some situations call for a professional’s touch.

Repeated Breakdowns

If your AC frequently breaks down, it’s best to call a professional. Persistent issues can indicate a more severe underlying problem that requires expert attention.

Major Fixes

Tasks like refrigerant refilling, serious electrical issues, or major component replacements should always be handled by a certified professional.

Regular Maintenance

Hiring a professional for regular maintenance can help detect and prevent issues before they escalate, enhancing your AC’s longevity and efficiency.

Why Is My Air Conditioner Running Outside but Not Inside

Preventive Measures

A few simple measures can help prevent issues with your air conditioner, ensuring it runs smoothly both inside and outside.

Regular AC Maintenance

Routine maintenance includes cleaning and changing filters, inspecting ductwork, and ensuring the system has adequate refrigerant.

Timely Repairs

Addressing minor issues promptly can prevent them from turning into major problems, ensuring uninterrupted comfort.

Optimal Thermostat Settings

Setting your thermostat to a consistent temperature can prevent unnecessary strain on your AC, enhancing its performance and lifespan.

Frequently Asked Questions

Why is the outside unit of my air conditioner running, but not the inside?

The inside unit of your air conditioner may not run due to a range of issues such as a faulty thermostat, power supply problems, blocked or leaking ducts, or frozen evaporator coils.

Can I fix my air conditioner myself if it’s running outside but not inside?

While simple solutions like checking the thermostat settings or resetting the circuit breaker can be performed by homeowners, more complex issues should be addressed by a professional.

How can I prevent my AC from running outside but not inside?

Preventive measures like regular maintenance, timely repairs, and maintaining optimal thermostat settings can help avoid such issues.


Air conditioners are intricate systems designed to enhance our home comfort. But issues like the unit running outside, but not inside, can disrupt this comfort. Thankfully, understanding the potential causes behind this peculiar situation can lead us to suitable fixes.

While minor issues can often be handled independently, more serious concerns require professional intervention. Ensuring regular maintenance of your air conditioner is paramount to avoid such problems and secure uninterrupted comfort.

Air conditioners are not just luxury appliances; they’re a crucial part of our homes, especially during the peak of summer. When they function as intended, we can enjoy a cool and comfortable environment. By staying informed about potential issues and their fixes, we can ensure our air conditioners keep serving us optimally.

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