If the blower on your furnace is running all the time whether your furnace is producing heat or not, you may need to call a furnace repair company to figure out why. Sometimes, simple things can cause this problem, but other times, you might need professional repairs on your furnace to get the blower to turn off. Here are four things that cause your furnace blower to run continuously.

1. Very Cold Weather

Before you call a furnace repair company, consider if the cold weather you're having is much colder than usual. If so, your furnace might be struggling to keep your house warm so it's running almost all of the time. If that's the case, there might not be anything wrong with your furnace. You might try adjusting the thermostat to a much lower setting to verify if the blower turns off.

Also, make sure the thermostat didn't get bumped from auto to the fan setting. Your blower runs all the time if the thermostat is set to fan, so if that's the problem, just switch the thermostat back to auto.

2. The Limit Switch Is Faulty

Your furnace has a limit switch that turns on the blower. When your furnace starts, the blower has a delay so it doesn't blow out cool air. Instead, when the air is warm, the switch turns on the blower. The switch is also responsible for turning off the blower. If the switch goes bad while the blower is running, it won't be able to turn the blower off and the blower will run continuously.

A furnace repair technician will replace a bad limit switch and ensure that it is able to turn the blower on and off as it should.

3. A Blown Fuse

A blown fuse allows the blower fan to run all the time. A furnace repair technician can replace a bad fuse easily. When the fuse blows, you'll usually see a burnt area on the plastic to verify the problem is the fuse. A fuse might be mounted on the inside of the furnace, hanging loose on wires, or attached to the control board. Replacing it is a matter of pulling the blown fuse out and putting a new fuse in its place.

4. An Overheating Furnace

Your furnace has a safety mechanism built in that shuts off the gas if the furnace is overheating. This shuts down the heat so your furnace is protected. However, the blower may not shut down. Instead, it can keep running all the time. A furnace repair technician has to figure out what's causing the furnace to overheat and why the safety mechanism stops kicking on.