WHAT DOES THE FAN DO IN AN AC UNIT?

As your air conditioning system cools the air inside your home, fans play a crucial role in maintaining airflow through the system and dissipating heat.

The two fan types in split-system central air conditioners are the blower fan, which sits in the indoor unit, and an outdoor condenser fan. Problems with either can lead to wider cooling problems due to restricted airflow issues— lack of cooling, frozen AC or extra strain on the system leading to premature AC repairs.

Let’s look closer at what the fan does in an air conditioning unit, the difference between ON and AUTO thermostat settings, and how you can optimize AC performance in your Florida home…

WHAT DOES THE FAN DO IN AN AC UNIT?

The blower fan in the inside air conditioning unit circulates air through the unit (over the evaporator coil) and throughout the home, ensuring that cool air is distributed efficiently. The fan motion can also help to maintain comfortable air quality. The outdoor condenser unit also contains a fan, which helps to dissipate heat from the refrigerant as it is compressed during the cooling cycle.

what does the fan do in an ac unit

STAY COOL ALL YEAR ROUND WITH ONE WAY AIR…

The team at One Way Air installs, services, and repairs all types of air conditioning systems in Southwest Florida. Get in touch with us here for a quote or call 239-233-4356 in emergencies.


HOW DO FANS IN AIR CONDITIONERS WORK?

An air conditioner works due to a continuous cycle of condensing and evaporating AC refrigerant. The compressor housed in the outside unit converts the liquid into a gas and the condenser converts the gas to a liquid. This process enables the refrigerant to absorb heat as it passes through the indoor unit’s evaporator coil and release it outside.

Air movement is central to this process—and that’s where the AC fans come in. 

how the cooling process works

INDOOR BLOWER FAN 

The blower fan is usually housed in the blower unit or indoor air handler of a central air conditioning system and is controlled by an electric motor. This fan is responsible for:

  1. Blowing warm indoor air across the evaporator coil during the cooling process.
  2. Pushing the cooled air into the ductwork as it circulates throughout your home.
blower fan ac unit

The AC blower fan does not cool the air in the home but works in conjunction with the cooling system to create a comfortable and consistent temperature, also helping to filter air and improve indoor air quality.

OUTDOOR CONDENSER FAN 

In the outdoor condenser unit, a fan helps to pull air over the outdoor condenser coil, allowing the refrigerant to cool and liquefy, releasing the heat absorbed from inside the home. 

condenser fan ac unit

AC FAN MODE SETTINGS: AUTO OR ON? 

One of the most common questions from homeowners about AC fans is “Should I set the AC fan mode to AUTO or ON?” 

The standard thermostat fan settings for the indoor blower fan are ON or AUTO but there’s no single answer to which one is best. 

AUTO mode means that the blower fan runs only during the cooling cycle. This usually provides a good balance of comfort, air quality, and energy usage, while also helping to control humidity in the home.

ac controls auto setting

ON mode is for continuous operation of the AC blower fan, leading to continuous air circulation and filtration even when the compressor is not running. The main downsides of this are higher energy usage costs and, potentially, overworking of the fan motor.

Setting the fan to AUTO is generally best for most Florida homeowners. However, setting the fan to ON can be beneficial when deep cleaning the home (extra filtration of dust, pet dander, etc.) or defrosting a frozen AC unit. You might also use this setting in mild weather when you just want additional airflow without cooling in the home—though it’s usually better to use ceiling fans in this situation.

If you do use the ON mode for the AC fan, remember to turn the setting back to AUTO afterward and to clean or change the AC filter regularly.

ac controls on fan setting

Bear in mind that running the fan continuously can add $20–$50/month to electricity bills, so there is a significant cost trade-off if you prefer that setting.

WHAT DOES THE FAN DO IN OTHER AC MODES

Depending on your AC setup, there may be other options than simply ON or AUTO for the fan and COOL/OFF for your AC. 

  • AC in Dry Mode doesn’t need to reduce the air temperature and the fan usually runs slower, simply removing excess moisture from the air in your home. This can be especially useful in humid climates like Florida.
  • In Power Saver, Energy Saver or Eco Mode, the AC turns off the compressor and fan when the target temperature is reached and turns them on again when the temperature rises. 
  • In Sleep Mode, the fan speed may reduce for lower noise and the thermostat temperature often increases in small increments every hour through the night to save energy.
ac controls sleep mode

TIPS FOR OPTIMAL AC FAN PERFORMANCE

The blower fan may not be the most expensive component in your AC system but, like all components, it can wear out if not regularly serviced.

AC costs in Florida are high so no homeowner wants to pay for a replacement before absolutely necessary. An annual AC tune-up should be in every homeowner’s diary as this will help to protect the investment.

In Florida’s heat and humidity, we ask our AC systems to work hard for a large part of the year. It’s essential to ensure that everything is in good working order before the summer comes.

ac summer Florida

Annual cleaning and lubrication from a professional can prevent many AC fan problems. Generally, too, homeowners should ensure continuous airflow in the AC system by changing the HVAC filter regularly and ensuring that vents and ductwork are clear of obstructions.

The U.S. Department of Energy estimates that dirty filters can increase AC energy use by up to 15 percent—so by maintaining your system properly you’ll save on monthly energy bills and lower AC repair bills.

annual ac maintenance

FAQs

Modern AC blower motors last 10–20 years. Setting the thermostat to continuous operation may slightly accelerate wear but regular HVAC maintenance should prolong the life of all AC components.

Unfortunately, running the AC fan alone does little for dehumidification as it simply circulates air already in the room/home. Keeping the fan on while the home is humid can actually worsen indoor humidity. With an AUTO setting, the fan works with the AC to cool and dehumidify the inside air cost-effectively, helping homeowners maintain ideal humidity levels for Florida.

Yes, a damaged AC fan is a common reason for ice on the inside AC unit because it can cause reduced airflow over the evaporator coil. A damaged condenser fan can also cause the outside AC unit to freeze up due to pressure imbalances, cooling inefficiency, and refrigerant issues.

Yes, if you are thawing a frozen AC unit, turning the fan setting to ON while the cooling is off (fan-only operation) can speed up the process. Make sure to catch any thawing water below the AC unit in a suitable vessel.

No, residential air conditioners generally recirculate the indoor air and do not ventilate the home unless specifically modified to bring in outside air. A separate fresh air intake or ventilation system (like an ERV or HRV) can introduce outside air to the AC system.

Indoor air can be 2–5 times more polluted than outdoor air. Running the AC fan can help filter dust, pet dander, and other contaminants from the inside air to some extent. However, for best results or if you have allergy sufferers in the home, consider installing air purifiers in the main rooms. 

An AC system may suffer from weak airflow for several reasons, usually connected to restricted circulation or airflow issues. This can be because of a dirty filter, frozen AC coils, a dirty or faulty blower fan or blocked ductwork.

Ceiling fans and air conditioning work well together to enhance indoor comfort and improve energy efficiency—just make sure your ceiling fan is turning in the right direction for the summer and winter seasons.

ceiling fan Florida

PROLONG THE LIFE OF YOUR AC UNIT 

Whether you need an AC tune-up or repairs, contact an AC professional at One Way Air for an inspection today.

More Articles Like This

Scroll to Top
Call Now: (239) 233-4356