Furnace Blower Fan Isn’t Turning Off? Here’s What to Do
The wheels on the bus go round and round all day long, and your furnace blower fan is trying to give them a run for their money. Take a look at the 4 steps in this article that will help you stop any furnace blower fan from running constantly.
If your furnace blower fan won’t turn off, try these steps:
- Turn the thermostat to “AUTO”
- Lower the thermostat temperature
- Turn the limit switch to “AUTO”
- Reach out to a professional
The steps mentioned above are so simple that you can have this job done in a matter of minutes. So, are you ready to try them out on your furnace blower? Then take a look below for more instructions.
Is your furnace’s blower fan working 24/7? You’ve turned the system off, waited, and it’s still blowing. You’ve turned it back on, then off again. But no matter what, the furnace blower just won’t quit.
Having the blower running non-stop is a bit of a concern. Of course, we immediately wonder what could be causing the problem. And most importantly, how much it is costing to keep the blower on all day.
But, before you call a professional, here are a few things you can try to make the blower turn off.
The first place you will need to look to fix this problem is at your thermostat. The blower fan will continue to run if the thermostat is set to “ON”. When it is set to “ON” the blower will run constantly regardless of whether it is in a heating cycle or not.
To fix this problem, do the following.
- Change the setting on the thermostat from “ON” to “AUTO”
- Wait for 3 to 4 minutes for the thermostat blower to turn itself off
Here is the second thing you can try to stop your blower fan. That is to lower the temperature on the thermostat. If the thermostat is set too high, the furnace will keep running. It will do so to try to heat the home until it reaches the desired temperature.
Here’s what to do.
- Lower the temperature using the dial or buttons on the thermostat’s interface. Take the temperature down 3 or 4 degrees.
- Wait 10 minutes for the furnace to start working to reach the new temperature. The furnace blower should stop after this time.
- If the blower fan is still running, turn the thermostat down further. During the winter, you may need to turn the thermostat down considerably for the blower to stop.
Have you completed the first two steps in this article? Are you still having trouble with your blower fan? Then try this third suggestion that should ground it to a halt.
This time, you will need to adjust the settings on the limit switch. If your blower fan is working constantly, your limit switch has one of the following problems.
- The switch is set to “MANUAL”
- The switch is faulty. You must have it repaired or replaced.
If your limit switch is set to “MANUAL” the blower fan will run continually. The switch could have been tampered with accidentally and put on “MANUAL”.
It is also possible that the system wasn’t tampered with. Rather, it may have set the limit switch itself to manual when the furnace overheated. When the furnace overheats, it will stop producing hot air. So, if your heater won’t heat but the fan runs, it is a good indication that there is something wrong with the limit switch.
But why did the system overheat in the first place? This could be the result of a number of issues. Take a look at just some of them below.
- A clogged air filter. Poor airflow could result in an overheating furnace. I recommend that you change your furnace’s air filter regularly. In some homes, the filter will need to be changed once a month. In others, changing the filter twice or only once a year is sufficient.
- Multiple vents are closed. If you have closed too many vents in the furnaces’ system, it could begin to overheat. To avoid this problem, you should keep every air vent open at all times. Doing so will make sure that every room in the house heats evenly. It will also help to reduce your utility bills.
Ok, so let’s get into the nitty-gritty of it all. That is, adjusting the settings of the limit switch. To do so, you’ll need to locate the switch first. You can find yours inside the panel cover of your furnace. Inside the panel cover, you should see a small white button. That is the limit switch.
Once you’ve located the switch, do the following.
- Check the position of the switch. Determine whether the switch is pressed in or pulled out.
- Check the printing on the switch to see whether you should pull the switch out or push it in to turn it off of “MANUAL”. The “MANUAL” setting will force the blower to continue running regardless of whether it is in a heating cycle or not.
- Reset the switch to “AUTO” by pulling or pushing on it. Follow the instructions* on the switch.
- *NOTE: Most switches when ‘pushed in’ are set to “MANUAL”. In this case, you will need to pull the switch out to set it to “AUTO”. But you should double-check the instructions on your switch to make sure you get this step the right way around.
- Wait 10 minutes. This should give the blower fan enough time to stop running
How can you know when it is time to call a professional to fix your furnace blower fan? You should call a professional if you have gone through all the steps mentioned below but your furnace blower fan is still running.
- You have tried changing the thermostat settings from “ON” to “AUTO” then waited for 3 to 4 minutes
- You have turned the temperature down on the thermostat then waited for 10 minutes
- You have adjusted the settings on the limit switch from “MANUAL” to “AUTO” then waited 10 minutes
If you have followed through all these steps, then you have really done everything you can do as a homeowner. It is now up to a professional to fix the problem. But what could still be the issue? Your furnace blower could have any of the following things wrong with it.
- The fan relay is stuck. You will need to have the control board or the relay replaced.
- The thermostat cable has shorted. There is a short in the wiring that is forcing the furnace blower to keep running. You will need to have the wiring repaired.
- The thermostat is faulty. The thermostat will not turn the temperature down so the furnace keeps running. You must have the thermostat replaced.
- The fan limit switch is faulty. The limit switch is set to manual and you cannot change it. You must have the switch repaired or replaced.
You do everything you can to turn your furnace off but, somehow, the blower fan is still running. Having it running constantly is a concern and not to mention, a waste of money.
Thankfully, this article has discussed 4 things you can do to fix this problem. I am sure it has helped you to turn your blower fan off or has helped you to know when it is time to phone a professional.
Have a great day!