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Troubleshooting an AC Fan that Won't Stop Running

Every homeowner gets a heating and cooling system expecting that it will serve them perfectly without exhibiting any problems. However, it can become a major issue when the AC fan doesn’t seem to stop when it should. Whenever your HVAC system stops working correctly, there is certainly a problem that needs to be addressed. While it is perfectly normal for the fan to kick on a few minutes before the system starts or stay on for a few minutes before it finally shuts down once the unit is switched off, it should not stay on for too long or run continuously.

Typically, your HVAC unit’s fan should have an off-on sequence at specific intervals and go off when the unit is shut off. The fan running continuously may not affect the fan negatively, but it could indicate something more serious is wrong that needs to be addressed urgently.

There are several reasons why your fan may continue despite being turned off. These include having a faulty thermostat, stuck relays, and poor wiring. While these are not typically DIY projects and must be handled by a professional HVAC technician, you need to know what to do whenever you experience such issues.

AC Unit Inspection & Repair

Normal Working of the AC Fan

The blower fan works together with the cooling and heating unis despite being a separate system. The furnace and air conditioner heat and cool the air around them, whereas the fan pulls all the unwanted and uncomfortable air out of the house and then passes it through the AC or furnace before redistributing it back to the house. These systems work together because of the thermostat, which directs the roles of each.

Whenever the thermostat is set on auto, which is often the typical case, it directs the fan and the heating/cooling elements to turn off once the desired temperature is attained. The on-and-off sequence needs to happen at the same time. Usually, most systems have the blower fan running for a few seconds before the heating or cooling unit starts to blow. This ensures that there is sufficient airflow. However, when you set the thermostat to the On position, the fan will run on its own, which should happen only temporarily, especially if you are trying to increase the circulation levels.

Top Issues that May Cause your Fan to Run Continuously

  1. Thermostat setting: You need to confirm that the thermostat is set on auto and not in the ON position.
  2. Extreme Temperature Situations. In cases where the environment is either too hot or too cold, the HVAC system may not get to the desired temperature. This often happens when the system is smaller in size for the home or when it has been neglected and not maintained properly. The fan can run continuously in such cases until the weather condition improves.
  3. A case of a faulty thermostat. This will be the case if both the fan and hot/cold system run continuously.
  4. A short circuit or broken relay situation. Whenever the fan is running alone, there is a possibility that there is a broken relay switch. A broken switch prevents any setting on the thermostat from being relayed to the fan. The same could happen whenever a wiring issue or a short circuit has occurred. In most cases, both problems affect the On and Off commands from being relayed to the fan.

How to Fix These Problems

Besides regular maintenance, you need to pay extra attention to your HVAC system and have it repaired whenever you notice strange sounds. Quick action is essential as it spares you the expense of replacing an entire HVAC unit, which is likely to happen if you ignore the numerous signs and indicators. 

Homeowners may not realize how issues like this can easily be prevented with simple regular maintenance. Investing in regular checkups and tune-up sessions ensures that you never skip any needed service and will help keep your HVAC system running smoothly year-round. 

Reach Out for Professional Assistance

The best you can do as a homeowner is to be observant. A problem like a continuous running fan needs to be addressed by a professional. Monitor and track any changes and signs and have your technician’s number on speed dial. Your HVAC technician will be able to diagnose and fix the trigger causing your HVAC unit’s fan to run continuously. In addition, the expert will also advise you on what to do or look out for next time.

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Customer Reviews

Called Absolute for my 81 year old landlord in the height of Summer heat. Scott came out to inspect the old beast of an AC and found many issues. He took the time to educate us, note everything, photograph it and provide several recommendations...and my stubborn landlord has done nothing LOL. A couple months later we asked that Scott come back out and he was there that same day.

Emily H.

Santa Ana, CA

I contacted Absolute Airflow to check my mother's AC, as it was not getting cold. The tech (Scott) arrived earlier than his scheduled time, and was very knowledgeable, professional, and most of very personable with my mother in letting her know that the issue was. Superb customer service Scott and thank you Absolute Airflow! I highly recommend Absolute Airflow.

Billy A.

Billy A.

Bellflower, CA

I have called in Absokite Airflow for my tankless water heater and A/C unit for maintenance. They were professional and took the safety precautions necessary including wearing a mask and cornering their shoes when entering my home. I recommend them highly. Shout out to Zack who took care of the tankless water heater.  They were professional and friendly.

Beatriz S.


Santa Fe Springs, CA

Carlos came to our house to access the A/C project and to give us an estimate. He was very knowledgeable and took his time to explain all the opinions in detail as well as the installation process and warranties. Tanner and Chris were the installers, they were very professional taking their time and attention to details. To keep our house clean while installing the new A/C system.

Robert M.

Robert M.

Whittier, CA