Why is My AC Fan Not Working?

Modern air conditioning... it’s a wonderful thing in the heat of summer when you can go inside and feel the relief from a hot, sticky summer day. That’s why it’s so upsetting to crank up your AC only to find the air conditioner fan not working, and the temperature in your home rising. But before you totally lose your cool, take a few minutes to troubleshoot and see if it’s a problem you can fix or if it’s time to call your local Carrier HVAC expert for professional air conditioner repair.

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8 Reasons Why Your AC Unit Is Not Working

Before you just assume it’s a bad fan, spend a few minutes determining whether other issues within your air conditioning system may be causing the problem. Your central air conditioner is a complex system with many components, and there are several issues that could be the reason your AC fan is not working.

1. Check Your Thermostat

Start by checking your thermostat. If the system is on, but set for heating instead of cooling, the system likely won’t operate. Switch it back to either cooling or auto mode (automatically switches between heating and cooling), and check that an appropriate cooling temperature is selected. According the Department of Energy,  78⁰F is a good setting for both comfort and energy efficiency when you are home.

If you have a programmable smart thermostat, check to be sure your comfort schedule is properly set for cooling at the time you are having the issue, and make adjustments if necessary.

2. Circuit Breaker is Tripped

If you are satisfied that the thermostat settings are correct, check your power supply. Your AC system runs on electricity, and there are typically three locations you can check to be sure the issue isn’t with power to the system. First, locate your main breaker box panel and make sure the AC system circuit breaker hasn’t been tripped. The outdoor unit typically takes 220v power to operate and should be on its own circuit. If that isn’t the issue, there is a power switch typically located on the air handler unit (furnace or fan coil) inside your home that looks similar to a light switch. It should be in the “on” position. If that’s not the issue, step outside and check the power disconnect for the outdoor unit. It is usually located in a separate box, usually mounted on the home near the outdoor unit. Make sure it is in the “on” position as well. If a fuse in this box is blown, that means it’s time to call your Carrier dealer for professional assistance.

If the issue is a tripped circuit breaker, keep in mind that it could have been caused by a power surge of some kind, possibly weather related. If the system continues to trip the circuit breaker, shut it down and call a professional HVAC technician.

3. Air Filter is Blocked

Another common and easily remedied situation that sometimes results in a central air conditioner fan not working is a dirty, clogged air filter. Your system’s air filter traps dust, dirt and other airborne pollutants to keep indoor air and internal cooling system components cleaner. If it’s not cleaned or replaced regularly, a clogged air filter can restrict air flow to the point that it feels like the indoor fan is not properly circulating air. In extreme cases, restricted airflow can cause the entire system to shut down. If this is the case, simply cleaning or changing the air filter should solve the problem.

For more information on changing the system’s air filter, and how often to do it, take a look at our air conditioner filter page.

4. Broken Fan Blade

If your system is running but you hear unusual noise coming from the outdoor unit, you might have a bad fan or a bent or broken fan blade. To troubleshoot, turn off the system at the thermostat as a safety precaution. A broken or damage fan blade can be dangerous if the system turns on while you are inspecting it. Once you have ensured the system is turned off, go outside to the outdoor unit. The condenser fan motor and fan are typically mounted at the top in the center of the unit and are usually visible through the fan guard or wire grill. If a fan blade is cracked, loose or broken, it can cause unusual noises due to it being out of balance or physically striking other components in the outdoor unit. If you discover a broken or damaged fan blade, keep the system turned off and contact a local HVAC professional for repair.

5. Burnt Out Condenser Fan Motor

If the fan blades seem to be ok, turn the system back on and check that the outside condenser fan motor is operating properly. Vibration or noisy operation would signal the fan blades are likely out of balance. If the fan blades don’t spin at all, it’s likely the condenser fan is not working and possibly burnt out, requiring replacement. In either case, we recommend calling a professional HVAC technician to diagnose and remedy the problem.

6. Frozen Evaporator Coil

Air conditioner fans not working can be a sign of a frozen evaporator coil. The evaporator coil sits inside your home within the air handler unit (furnace or fan coil), pulling heat and humidity from indoor air as it passes through. The evaporator coil can freeze up as a result of indoor blower fan malfunction, low refrigerant charge, low outdoor temperatures, or other system malfunctions. Because a frozen evaporator coil can be the result of a blower fan stoppage or the reason the blower fan stops running, a frozen coil with fan stoppage should be diagnosed and remedied by your local Carrier expert.

7. Compressor is Not Working

Many of the malfunctions already discussed can ultimately damage the compressor. Your AC system’s compressor is mounted inside the outdoor unit and is responsible for circulating refrigerant through the system’s copper tubing and coils. If the power to your AC unit is on, and the thermostat is set properly, yet there is no noise coming from the unit, the problem may be a damaged or malfunctioning compressor. Replacing a compressor is a major operation, which should be performed by a licensed and experienced HVAC technician. This will likely also raise the question of whether it is time to replace the entire unit or do the repair.

8. Malfunctioning Run Capacitor

The outdoor unit of your AC system includes a smallish metal cylinder called a run capacitor that plays a large role in your system’s functioning. The run capacitor controls and supplies the electrical charge that starts and continues to operate the unit’s fan motor. If a run capacitor malfunctions, your AC system may not start, or it might start but continue to run, possibly making a humming sound. Other signs the run capacitor has malfunctioned include slow or delayed start-up, system shut down, or the system not blowing cold air. If you suspect a faulty run capacitor is the cause of your air conditioner fan not working, contact a professional HVAC service tech. Capacitors can retain electrical charge and should only be replaced or handled by a licensed and trained professional.