Troubleshooting a Furnace Blower Motor with Humming Sound

A furnace blower motor is one of the important components in your gas or oil furnace. The home furnace provides much needed heat during winter so it is a good idea to check it in autumn. This way you can fix any problems before the cold winter days set in. The furnace blower directs the warm air created inside the furnace to your house. It is necessary that this blower is performing at its optimum. Otherwise, you will not only get reduced heat but also be wasting energy.

Basic Troubleshooting
One of the most common problems of blower motors is a humming sound. If this is your problem, then the first thing you should do is turn off your motor and allow it to cool. When it has cooled down to a safe temperature, check the motor. Insufficient lubrication may also be a cause of the humming from your blower motor. Try lubricating the motor but remember not to over-lubricate it. If this does not work, proceed to the following options.

Humming at Slow Speeds
When your furnace blower has warmed your house to the set temperature, it begins to run on a slower speed. Does you blower motor slow down unusually? Does it make a humming sound when it has slowed down? This might be due to a fault in the capacitor and the motor. Check your motors amperage draw. The rating on the plate of your motor will tell you how much is required. If the draw is more than the required amount, it is an indication that your motor is working extra hard to work. You will have to replace the motor and the capacitor. This problem in your motor may have been caused by dust and dirt in your filter. An unclean and blocked filter makes the motor work harder to push out air. Make sure you check and clean the filter regularly to avoid this kind of problem from recurring.

Motor Humming without Turning
If your furnace blower motor makes a humming sound when it is switched on but does not turn, the capacitor may be damaged. This is a very common problem with motors that do not have good quality capacitors. You should replace the capacitor with a good one and the blower motor will work smoothly. Once again, this may initially have been caused by of a blocked filter. If your motor does not run even after replacing the capacitor, it is most probably because of the unit had overheated. You should reset the safety buttons located at the side of the unit.

Humming when the Blower is Off
This is usually caused by the wrong adjustment of the pilot light of your blower. Readjusting it to an appropriate level should solve this issue.

Humming when the Blower is On
If your gas burners are dirty, they will give out a low sound that may sound like something between a low rumble and a hum. Cleaning, adjusting or replacing them will make the irritating sound go away.

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