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Why Does My AC Condenser Keep Running?

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Air conditioning units are crucial for maintaining comfort in our homes, especially during the hot summer months. However, a common issue many homeowners face is a continuously running AC condenser. In this comprehensive guide, we delve into why your AC condenser might keep running and how you can address this issue.


Your AC condenser might keep running due to several reasons including dirty or blocked condenser coils, a dirty air filter or evaporator coil, low refrigerant levels, a faulty thermostat, electrical issues, a stuck AC contactor, or an undersized AC unit. To address this, you can check the thermostat, clean the condenser coils, ensure the outdoor condenser unit is free from debris, check refrigerant levels, or replace the air filter. If the problem persists, it’s advisable to call a professional HVAC technician.

Understanding the AC Condenser

The AC condenser plays a pivotal role in the cooling process of your air conditioning system. Its function is to lower the temperature of the refrigerant, allowing it to transform back into a liquid. This process involves dissipating heat carried to the outdoor unit, enabling the cooling process to continue.

However, several issues can cause the AC condenser to run non-stop. Let’s explore these problems in detail.

Common Causes of a Continuously Running AC Condenser

  1. Dirty or blocked condenser coils: When the condenser coils are covered in dirt and grime, the unit has to work harder, causing the fan to run constantly.
  2. Dirty air filter or evaporator coil: A dirty air filter or evaporator coil can reduce the cooling capacity of your AC, causing it to run continuously.
  3. Low refrigerant levels: Low refrigerant levels can cause your AC to run constantly because it’s unable to efficiently cool your home.
  4. Faulty thermostat: A malfunctioning thermostat may not be able to accurately sense the temperature, causing the AC to run continuously.
  5. Electrical issues: A stuck relay switch or a short circuit can cause the condenser unit to keep running with constant power.
  6. Stuck AC contactor: A stuck compressor contactor in the outdoor unit can cause the fan to run continuously.
  7. Undersized AC unit: If your AC unit is too small for your home, it may struggle to keep up with the cooling demands, causing it to run constantly.

Signs of a Continuously Running AC Condenser

If you suspect your AC condenser is running non-stop, here are some signs to look out for:

  1. Uneven temperatures: If you have a hot upstairs and a cold downstairs, it could be a sign that your AC is struggling to keep up with the influx of outside air.
  2. Dirty condenser coils: A quick visual inspection of the outside unit can reveal if the condenser coils are covered in dirt and grime.
  3. Frozen evaporator coil: If your unit is blowing warm air from the supply vents, in addition to running constantly, it may have a frozen evaporator coil.
  4. Restricted airflow or low blower speed: This can be caused by a dirty air filter, which restricts the airflow to the indoor part of your AC.
  5. Dirty evaporator coil: If your inside unit’s evaporator coil is dirty, it makes it tough for the refrigerant to absorb heat from your air.

Troubleshooting a Continuously Running AC Condenser

Before calling in a professional, there are several steps you can take to troubleshoot a continuously running AC condenser:

  1. Check the thermostat: Ensure that the thermostat is functioning properly and set to the correct temperature.
  2. Clean the condenser coils: If the condenser coils are dirty, clean them to improve airflow and cooling efficiency.
  3. Check for blocked outdoor condenser unit: Ensure that the outdoor condenser unit is free from debris, which can block airflow.
  4. Check refrigerant levels: If the coolant levels are low, refill the coolant if necessary.
  5. Replace the air filter: If the air filter is dirty, replace it to improve airflow.

When to Call a Professional

If the problem persists despite your troubleshooting efforts, it’s time to call a professional. A professional HVAC technician can perform various tasks to resolve the problem, such as cleaning the condenser coils, checking and fixing refrigerant leaks, inspecting and repairing or replacing the AC contactor, and assessing and fixing any ductwork issues.

In conclusion, while a continuously running AC condenser can be a cause for concern, understanding the potential causes, signs, and solutions can help you address the issue efficiently. Regular maintenance of your AC unit can help prevent many of these issues and ensure that your AC runs efficiently.

Frequently Asked Questions

How often should I clean my AC condenser coils?

Ideally, you should clean your AC condenser coils once a year. This helps to maintain the efficiency of your AC unit and prevent problems like a continuously running condenser.

How do I know if my AC unit is undersized?

Signs of an undersized AC unit include the unit constantly running, failing to reach the desired temperature, uneven temperatures in different rooms, and higher than usual energy bills.

Can a faulty thermostat cause my AC condenser to run continuously?

Yes, a faulty thermostat can cause your AC condenser to run continuously. If the thermostat cannot accurately gauge the temperature, it may keep signaling the AC to cool, even when it’s not necessary.

How often should I replace my air filter?

The frequency of replacing your air filter depends on the type of filter you use. However, a general rule of thumb is to replace it every 60-90 days. If you have pets or someone in your home has allergies, you may need to replace it more frequently.

What is an AC contactor and how can it cause my AC condenser to run continuously?

An AC contactor is a switch in your outdoor unit that turns the air conditioner on and off. If it gets stuck in the ‘on’ position, it can cause the condenser to run continuously.

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