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A Brief Guide: How To Replace The Motor In The Blower Fan On An Average Furnace

by Harvie Simms

One sure sign that a blower motor is going bad is that it will kick on and off. If you notice this happening with your furnace, you should also check to see if the motor is getting hot. A bad motor will often be humming and hot to the touch. You should replace the motor as soon as possible to make sure the furnace will be fully operational when you need to use it again. Here is a brief guide on how the motor of the blower fan is replaced on the average furnace.

Safety First

Make sure you turn off the electricity and gas going to the furnace. There is usually an electrical switch along the side of the furnace that you can switch off, but for extra safety, you should also turn the circuit breaker for the furnace to the "off" position, too. The gas valve is typically located on the gas line just as it enters the furnace. Turn the valve handle so it is perpendicular to the gas line to shut off the gas.

Remove Blower Unit

Most furnaces have the blower located on the bottom of the furnace and it will have its own access panel door. Remove the door. Sometimes there are a couple of screws you'll have to remove first, but other times you just lift up on the panel to slide it off the furnace.

The blower unit is typically bolted to a bracket inside the furnace. Remove the bolts to the bracket and disconnect the electrical wires going to the fan motor. If you have a phone that takes pictures, you should take a picture of how the wires for the motor are connected to the electrical control panel. You can refer back to the picture to make sure you are putting the right wires back in the correct spots when you put the new motor into the furnace.

The blower unit should slide right out of the furnace once the bolts and wires are removed.

Remove Motor from Blower Unit

Inside the blower unit is the motor shaft. Remove the nut and washer on the shaft and then flip the blower unit over. On the backside of the blower unit is the motor bracket. The bracket is connected to the blower unit with three or four bolts – depending on the model of the furnace. Remove the bolts to the bracket and slide the motor out of the blower unit. Remove the motor from the bracket.

Install New Motor

Attach the new motor into the bracket and reconnect the bracket to the blower fan. Insert the fan back into the furnace and bolt it back to the furnace. Use the pictures you took to make sure the wires from the motor are properly reinstalled into the control panel. The wires will have different colors that will help you know where each one goes. Turn the power and gas back on and start up the furnace. Wait until the furnace kicks on and starts the blower fan to circulate air through the duct system. Put the panel back on the furnace to finish the job. If you don't feel comfortable making these changes on your own, contact a furnace repair expert in your area.