Why Is the Fan Running with No Heat?

Have you been noticing an issue with your furnace fan blowing without heat? Before you get overly concerned about a potential problem with your furnace system, you should check and make sure your fan setting on your thermostat is set to “AUTO” rather than “ON.” Then, turn the thermostat to a lower setting than room temperature and wait a few minutes to see what happens.

The “ON” setting will keep your furnace fan running even when it’s not needed, while “AUTO” will only have it running when needed to maintain your settings. If your fan is still running after you’ve taken the above steps, then there are several potential problems. Your fan limit switch might have been set to “manual override,” or that switch could be faulty altogether. You might also have an issue with your thermostat wiring that prevents you from changing the settings at the thermostat.

Only a professional will be able to fix and replace a faulty fan limit switch or bad thermostat wiring. However, before calling a technician, you can at least check to see what the fan limit switch setting is, and switch it away from “manual override” if that is the issue. Here’s a quick overview of the steps you’ll need to take to do that.

Find the fan limit switch

First, you’ll need to find where your fan limit switch is located. This will usually be inside the furnace panel cover, close to the upper right corner. This switch is what controls when the blower turns on and off, so if it’s properly working, the fan should turn on several minutes after the thermostat sends the signal for heat, and turn off several minutes after the heating cycle comes to an end.

However, if the fan is running nonstop regardless of whether or not the furnace is producing heat, the limit switch is either set to manual, or is faulty.

Check the setting

The fan limit switch will have a small white button on its lower left corner. This button is what determines whether the switch will operate manually or automatically. When set to manual, it will run until you stop it. When automatic, it will only run during heating cycles. Take a close look at the button—if it’s pressed in, then it’s set to manual, and that’s why your fan is constantly running. Set it to AUTO and wait and see if that resolves the issue.

Call for professional help if that doesn’t work

If the fan continues to run continuously even after you’ve successfully changed the fan limit switch setting, then either the limit switch is busted or you have a problem with your thermostat wiring. In either case, you’re going to need to seek professional assistance, as this is a much more difficult type of job that should only be taken on with professional tools and training.

For more information about dealing with heater fan issues in Mabank, TX, contact the team at Ken’s Comfort Zone Air Conditioning today.

Categorised in: Heating Repair

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