How to Replace a Furnace Blower
If you have forced heat in your home, the mechanical object that moves the heat from the furnace into the rooms is called the furnace blower. It is the furnace blower motor that powers the fan to push the air from room to room. Most furnaces that have been installed in the last twenty years use a direct-drive blower motor.
Troubleshooting
First, we will troubleshoot repairs for the direct-drive furnace blower. Testing and diagnosis would be similar for a belt-drive blower motor, but the replacement instructions are different.
If you think your furnace blower motor is bad, you should investigate to make sure it does not work before you purchase another one to replace it. Begin your initial diagnosis by shutting off the power to the furnace. Then, try to move the blower blades by hand.
Proper Lubrication
If the furnace blower motor will not spin freely, check to see if it has oil ports on the blower. If it has oil ports, you should add a few drops of oil to see if it helps the motor to spin freely. On either the belt-drive motor or the direct-drive motor, look for lubrication holes on the motor and on the blower pulley on belt-drive units. With your oil can, squirt a few drops of SAE-20 non-detergent oil (3 in 1 in the BLUE not the RED can) at the ten o’clock and two o’clock positions.
Do not use WD-40 lubricant on these ports as WD-40 will not help here. If there are no oil ports (to add lubricant) or the motor blades do not move easily after adding oil, the motor should be replaced. If your motor has an odor or smokes it is ready for replacement.
Removing the Furnace Blower Housing
Before you remove the motor you need to remove the housing and make diagrams of all the parts. Begin by making a diagram of all the wires and the colors that go together. New furnaces have a control board that all the wires connect to while older furnaces include a control box that uses a relay and wire connectors.
Next, you need to make a diagram of all nuts and bolts on the housing. If you have different sized bolts this is very important. If you want the diagram to work easier label your map and your bolts with numbers. Use a white or silver marker to write a number on the bolt and correspond it to the place on the map. Of course you will then actually remove the bolts from their holes.
Remove the Motor from the Housing
Removing the motor from the furnace blower housing is actually simple. Start by removing the screw that attaches the motor to the wheel. Next, remove the bolts on the motor mount. These bolts hold the motor to the furnace blower housing. Finally, pull the motor out of the housing.
The next step is removing the mounting bracket from the blower motor. Look to see how and where the bracket is attached to the motor. This might be another good time for a diagram. These things can look very confusing when it is time for reassembly. Keep in mind that older models often have the mounting bracket welded or attached permanently to the motor. In this case you will have to buy a motor that has the same setup or you could purchase a standard adapter kit.
Choosing the Replacement
The next part of the process is buying a replacement furnace blower motor. However, in most cases you should probably order the unit before you remove the old one. In any case, you can order your replacement motor online or over the telephone from your motors manufacturer. Find the motor model on the motor so that you can give it to the company representative.
If you have an old furnace you may run into problems. Many manufacturers discontinue parts after a few years. In this case you would need to order a universal motor and any adapters that are needed. If you do order a universal replacement there are a few things you need to know. Gather the following information before trying to order:
• Drive Type, belt or direct
• Diameter of motor in inches
• Horsepower
• Voltage
• Number of Speeds
• RPM Speed
• Forward or Reverse Direction
• Run capacitor Size
• Method for Mounting
Installing the New Motor
Installing the motor should be the easy part of the furnace blower motor replacement. However, there are a few things you should do to ensure that the process is as easy as possible.
• Make sure that the wheel of the motor is centered within the blower housing.
• Place the motor the correct direction for rotation.
• Isolate any extra wires using wire nuts or black electrical tape.
• In most cases you should replace the run capacitor when replacing the motor.
If everything is prepared you can simply reverse the removal process in order to replace the motor. Start by attaching the motor bracket to the motor. Next, attach the motor to the housing and reinstall the housing. Finally, check the unit for proper operation.
Start checking the unit b feeling of every register to make sure air is blowing. Next, listen to make sure that the unit sounds right. There should be no squeals or grinding noises. If you do hear noises or smell smoke there is something wrong with the installation.
Regular Maintenance
Ever year your furnace should have maintenance completed. This should include a check of your furnace blower motor. Check to see that air is blowing at the same speed as the previous year. Oil any ports on or near the motor. Check all the belts to ensure there are no cracks, chips, or tears. You should also check that the tension of the belt is correct.
One of the biggest problems with a furnace is when the blower motor fails. However, as you can see the process is actually simple to remove and replace this motor. If you need a new replacement furnace blower, you can shop online. This will save you 30-40% on the part and then you can hire someone to install it if you are uncomfortable doing the job yourself.