Your air conditioner can’t cool your home without the work of the AC fan. Fans are so important that your system has two of them. This guide explores why they are so important, how to determine which one is having a problem, and nine reasons one of them may not be working, and how to solve it.
The Role of Fans
All fans move air, including those attached to your air conditioner. While the refrigerant transfers heat inside your home to the air outside, it can’t do this without sufficient airflow.
Inside your home, the circulating fan moves air through the system where the refrigerant absorbs heat, pushing cooler air back out. Outside your home, the fan draws air through the condensing unit where the coil transfers the heat absorbed inside to the air moving through the coil. When one of the fans malfunctions, it will either prevent the system from cooling the air inside or venting the heat outside.
Determining Which Fan Has a Problem
Before exploring the problems and potential solutions, identify which fan isn’t working. Check which fan is running or if unusual sounds are coming from the indoor or outdoor unit.
Finally, visually check the outdoor unit to see if the system is running and look to see if the fan is spinning. You should be able to see this without putting your face directly over the unit. You likely won’t be able to see if the circulating fan is spinning or not.
1. Thermostat Settings
Your thermostat acts as your system’s brain, calling for cooling cycles and terminating them at the right time. However, if it’s not set correctly, it may prevent the system from engaging, including both fans.
Start by checking that the thermostat is set to cooling mode and the fan is set to Auto. Next, check if it’s running temperature programs and if they are set to the right time. Make sure your thermostat is set to the correct time and day.
2. Circuit Breaker or Power Disconnect
Every air conditioner typically has two dedicated circuit breakers: one that controls the indoor unit and one for the outdoor unit. Circuit breakers may trip when there’s a surge, usually caused during a significant thunderstorm or when there’s damage to the grid. There is a power disconnect outside for service technicians to disconnect the power when working on the unit.
Start by checking that both circuit breakers are in the “on” or closed position. If you find a tripped breaker, reset it and watch to see if it trips again. If it does, call for a technician to troubleshoot the issue. Additionally, check the power disconnect outside to ensure it’s set to allow power to flow through the circuit.
3. Burned-Out Motor
AC fan motors will eventually wear out and need replacing. Ignoring regular filter changes and forgetting routine maintenance will accelerate the wear.
A burned-out motor may emit an unusual sound or produce a burning smell. If you suspect you have a bad fan motor, it’s best to turn off the system and call for a professional to evaluate the system.
4. Worn-Out Capacitor
A capacitor is an electrical component that stores a large electrical charge, usually used to help power a high-draw motor. Most systems have a start capacitor to deliver the power needed to start the motor and compressor. Some systems also have a run capacitor to keep the system running.
If you have a worn-out capacitor, it may emit a loud hum when the system is trying to start. It’s dangerous to attempt to replace a capacitor without proper training, so call a professional if you suspect this problem.
5. Faulty Contactor
The contactor is like an automatic switch in the outdoor unit. When the thermostat calls for a cooling cycle, it sends a low-voltage signal to the contactor. The contactor closes the circuit, allowing the power from the capacitor to travel to the fan motor and get started.
Contactors may also go bad before the end of the air conditioner’s service life. A key indication of a faulty contactor is what sounds like a chattering coming from the outside unit. Because of the large electrical charge in the system, this is best left to a professional to evaluate and replace if needed.
6. Worn or Broken Belt
Older systems have a belt that drives the compressor and fan. If this belt is broken or excessively worn, it may prevent the fan from functioning properly.
Most air conditioners have an expected service life of 10 to 15 years. If you have one that’s belt-driven, it’s likely well beyond this age, which means it’s also likely using a prohibited refrigerant. If that’s the case, it may be time to consider upgrading your AC to get higher efficiency and better comfort, and reduce the repairs needed.
7. Dirty Air Filter
A dirty air filter is the underlying culprit for many AC issues. A clogged air filter restricts the airflow into the system, causing excessive strain and wear.
When the system senses the additional strain, it may shut down to protect the compressor. As the system shuts down, it will stop the circulating fan inside and the condensing unit fan outside.
For almost all AC issues, start by inspecting the filter and ensuring it’s not caked with dust and dirt. Ideally, check your filter every month to prevent an airflow restriction. For the common 1- and 2-inch filter, expect to replace it every 30 to 90 days. This range depends on your home’s air quality, filter construction, and how frequently it cycles.
8. Compressor Problems
The compressor regulates the refrigerant pressure in the condensing coil, allowing the system to vent the heat absorbed from the air inside. This can sustain damage from too little refrigerant, damage from age, power surges, and more.
When the compressor isn’t working properly, it may prevent the system from running, including keeping the circulating and condensing unit fans from running. If you suspect compressor problems, turn your system off and call a professional to inspect it.
Trying to inspect it yourself is dangerous because of the stored electrical charge and the risk of severe electrical shock or electrocution. Additionally, attempting to test the compressor without the proper training and tools risks further damaging the unit.
9. Fan Obstructions
Finally, the fan may have something physically obstructing it, preventing it from spinning. This most commonly happens with the outside condensing unit fan. However, in some cases, it may happen to the inside fan.
If you see something in the outside fan housing, turn off the power at the breaker before attempting to remove it. If you suspect something’s obstructing the inside fan, call a technician to come inspect the unit and possibly perform routine maintenance. Choosing to have a professional come out protects any warranty your unit may still have.
Keep Your AC Humming with Help From Us!
Homeowners in Duncan, Greenville, and the surrounding areas have relied on Tuck & Howell, Inc. to keep their homes comfortable since 1969. Our teams provide heating and air conditioning maintenance, HVAC repair and installation, and indoor air quality solutions. Call to schedule a maintenance or repair visit with one of our NATE-certified technicians today.
