Keeping Your Home Cool during the Sweltering, Summer Months

5 Causes Of Furnace Blower Failure

by Anthony Graves

The furnace blower is the heart of your furnace, as this is what pushes that warm air through your house. There are a few reasons a blower can fail. Identifying the cause is necessary in order to know the proper furnace repair.

1. Bad Limit Switch 

A limit switch is what controls the operation of the blower. When the temperature in the house drops sufficiently below the preset level, the limit switch flips the blower on. It then switches the blower off once the correct temperature is reached. Eventually limit switches will fail due to repeated use, and they tend to fail when the blower is in the off position. Replacement of the switch is all that's needed.

2. Poor Lubrication

The blower assembly includes several moving parts, including a set of bearings. These need to be well lubricated or the blower motor or fan may seize up and stop working. The time to lubricate is during your annual furnace maintenance and inspection appointment. By lubricating annually you can greatly increase the life and efficiency of your furnace blower.

3. Dust and Dirt

A lot of air moves through the furnace blower, and with that air comes some dust and dirt. Changing the filters on your furnace often helps but doesn't eliminate all dirt. This dust can coat the motor or even gum up the fan so it no longer moves smoothly. Dust can also lead to friction and heat, which can cause a blower to shut down before the heating cycle ends. Cleaning is a normal part of an annual maintenance appointment.

4. Electrical Problems

Your furnace should be on a dedicated circuit to prevent overloading. Ideally, it should also have a surge protector installed. If your blower keeps shutting down or tripping circuits in the house whenever it switches on, then the power supply needs to be checked. This includes verifying that the voltage supplied is correct and consistent, along with putting the furnace on a dedicated and surge-protected circuit.

5. Failed Belt

A furnace blower is basically a small engine connected to a fan. Belt-driven blower motors are relatively common. Over time, the belt will begin to stretch out and fray, which can lead to a blower that stops and starts or moves at an inconsistent rate. Eventually, the belt will give out completely and the blower won't come on at all. Replacing the belt is a quick and inexpensive repair. 

Contact a furnace repair service if you suspect issues with your furnace blower.