Why is My Furnace Fan Blowing Constantly?

If you’ve noticed that your furnace fan is blowing constantly, you might be wondering what the cause of this issue is. A furnace fan that runs continuously can be a sign of various underlying problems. In this article, we will explore the potential reasons why your furnace fan is blowing constantly and discuss possible solutions to help you troubleshoot and resolve the issue.

Fan Setting on Thermostat

The first thing to check is your thermostat settings. Ensure that the fan is not set to the “ON” position, as this will cause the fan to blow continuously. In the “AUTO” mode, the fan should only run when the furnace is actively heating your home. Adjust the thermostat settings accordingly and see if it resolves the problem.

Fan Limit Switch Malfunction

A faulty fan limit switch could also be the culprit behind a continuously running furnace fan. The fan limit switch is responsible for turning the blower on and off based on the temperature inside the furnace. If the switch is stuck in the “ON” position, it will keep the fan running constantly. In this case, it is essential to contact a professional HVAC technician to inspect and replace the faulty switch if needed.

Dirty Air Filters

Clogged or dirty air filters can lead to restricted airflow, causing the furnace to overheat. When this happens, the fan may run continuously as a safety measure to prevent any potential damage. Check your air filters and replace them if they are dirty or clogged. Regularly changing your air filters is crucial for maintaining the efficiency and longevity of your furnace.

Thermostat Malfunction

A malfunctioning thermostat can also contribute to a constantly running furnace fan. If the thermostat is not accurately detecting the temperature in your home, it may signal the fan to continue running even when it is not necessary. Consider replacing the thermostat or consulting an HVAC professional to diagnose and address any thermostat issues.

Wiring or Control Board Problems

Faulty wiring or a malfunctioning control board can cause the furnace fan to run continuously. The control board serves as the “brain” of your furnace, coordinating the various components. If there is a problem with the wiring or control board, it can disrupt the normal functioning of the fan. It is advisable to contact an HVAC technician to assess and fix any wiring or control board issues to ensure proper fan operation.

By addressing these potential causes, you can troubleshoot and resolve the issue of your furnace fan blowing constantly. However, since furnaces are complex systems, it is always recommended to seek professional assistance if you are unsure about troubleshooting or if the problem persists. An HVAC technician will have the expertise to diagnose the problem accurately and provide appropriate solutions, ensuring the efficient and safe operation of your furnace.