Does Air Conditioner Fan Always Run?

Air conditioning systems keep our homes cool and comfortable, especially during hot summer months. A key part of these systems is the fan. You might wonder if the air conditioner fan always runs or if it should only run at certain times. Let’s dive into these questions to understand how the AC fan works and the best practices for using it.

How Often Should an AC Fan Run?

The AC fan should run depending on the settings of your air conditioning system. Here are the two main settings:

  1. Auto Mode: In this mode, the fan runs only when the air conditioner is actively cooling the air. Once the desired temperature is reached, both the cooling system and the fan turn off. This mode is energy-efficient and can help extend the lifespan of your AC system.
  2. On Mode: When set to “on,” the fan runs continuously, even when the cooling system is not actively cooling the air. This can help circulate air throughout your home, but it uses more energy.

Most experts recommend using the “auto” mode for regular use to balance comfort and energy efficiency.

What to Do if the AC Fan Won’t Turn Off?

If your AC fan won’t turn off, there might be a few reasons why this is happening:

  1. Thermostat Settings: Check if your thermostat is set to “on” instead of “auto.” If it is, switch it to “auto” to see if that resolves the issue.
  2. Thermostat Issues: Sometimes, the thermostat might be faulty or need new batteries. Try replacing the batteries or resetting the thermostat.
  3. Stuck Relay Switch: The relay switch in your air conditioner controls the fan’s operation. If it’s stuck, the fan might keep running. This issue usually requires a professional technician to fix.

If the fan continues to run despite checking these factors, it’s best to call a professional HVAC technician to diagnose and repair the problem.

Why Is My Fan Running When My Thermostat Is Off?

If your fan is running even when the thermostat is off, there could be several reasons:

  1. Fan Setting: Ensure the fan setting on your thermostat is set to “auto” and not “on.”
  2. System Malfunction: There might be a malfunction in the control board or wiring that is causing the fan to run continuously. This typically requires professional repair.
  3. Delayed Fan Shutoff: Some air conditioners have a feature that keeps the fan running for a few minutes after the cooling cycle ends to help circulate the remaining cool air.

Does Leaving Your AC Fan On Save Money?

Leaving your AC fan on continuously does not save money. In fact, it usually increases energy consumption and costs. Here’s why:

  1. Continuous Operation: A continuously running fan uses more electricity because it never gets a break. This can lead to higher energy bills.
  2. Wear and Tear: Running the fan all the time can cause more wear and tear on the fan motor, potentially leading to more frequent repairs and a shorter lifespan for the fan.

For most homes, using the “auto” setting is more cost-effective and efficient.

Is It Better to Leave Air Conditioning on Auto or Fan?

Caucasian Men Setting Residential Modern Wall Thermostat to Lower Temperature To Save Energy During Winter Time Colder Days.

Choosing between “auto” and “fan” depends on your specific needs and preferences. Here are the pros and cons of each:

  1. Auto Mode:
    • Pros: Saves energy and money, reduces wear and tear on the fan, and maintains consistent temperature control.
    • Cons: Might result in less air circulation when the cooling system is not running, which can be an issue in homes with poor airflow.
  2. Fan Mode:
    • Pros: Provides continuous air circulation, which can help improve air quality and even out temperatures in different rooms.
    • Cons: Uses more energy, increases wear and tear on the fan, and can lead to higher electricity bills.

For most people, using “auto” mode strikes a good balance between comfort and energy efficiency.

When to Use the Fan Mode

There are times when using the fan mode can be beneficial:

  1. Allergy Season: Running the fan continuously can help filter and circulate air, which might reduce allergens.
  2. Balancing Temperatures: In homes with temperature differences between rooms, the continuous fan can help even out the temperature.
  3. Humidity Control: In very humid climates, running the fan can help reduce humidity levels by continuously moving air.

Maintaining Your AC Fan

Regular maintenance is essential to keep your AC fan running efficiently:

  1. Change Filters: Replace air filters every 1-3 months to ensure good airflow and reduce strain on the fan.
  2. Clean the Fan: Dust and debris can build up on the fan blades and motor. Clean these parts regularly to keep the fan running smoothly.
  3. Check for Issues: Listen for unusual noises and look for any signs of wear or damage. If you notice anything out of the ordinary, call a professional technician.

Improving Air Circulation Without Running the Fan Continuously

If you want to improve air circulation without leaving the AC fan on all the time, consider these alternatives:

  1. Ceiling Fans: Use ceiling fans to help circulate air in individual rooms. They use less energy than running the AC fan continuously.
  2. Box or Oscillating Fans: Portable fans can help move air and improve comfort in specific areas of your home.
  3. Natural Ventilation: Open windows and doors when the weather allows to let fresh air circulate through your home.


Understanding how your air conditioner fan works and the best practices for using it can help you maintain a comfortable and energy-efficient home. While the fan doesn’t always need to run continuously, there are times when using the fan mode can be beneficial. For most homeowners, the “auto” setting provides the best balance between comfort, energy savings, and system longevity. Regular maintenance and considering additional methods for air circulation can further enhance your home’s comfort and efficiency.

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