Real Plumbing Help

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Let’s take a look at an actual Lennox furnace motor replacement performed by a heating professional. This particular furnace has a gas valve with a built-in spark ignition. Problems with gas valve ignitions require professional help. If your Lennox furnace is having gas valve and ignition issues, contact a local heating professional for assistance.

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Furnace motors blow out for many reasons, including neglect as is suspected in this case. Unfortunately, many people are unaware of the importance of regular gas furnace cleaning and servicing. If you have a gas or oil furnace, it should be cleaned and serviced yearly to ensure efficiency and prevent problems such as a blown out motor.

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In addition, the air filter, which you can see in this picture as a blue, U-shaped object, should be cleaned or replaced monthly. Failing to clean and maintain the furnace and its filter reduces the life of the furnace, its controls, and the furnace blower motor as well as poses a fire risk. In addition, dirty filters and furnaces must work harder, which uses more energy than necessary.

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Here’s a close up picture of the gas valve. Just beyond the gas valve, you can see the cam stat which is responsible for starting and stopping furnace firing as well as for turning the furnace blower motor on and off.

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Now, let’s cut some wires, taking extreme care to cut the right ones. Again, double check to be sure that there’s no power to the furnace. Even if you know you turned off the power at the circuit breaker, is there a chance that someone has turned the power back on? If so, don’t risk it! Use your meter to double check and be sure. The Lennox furnace we’re working on has a 3-speed motor. Your furnace may have a single speed motor, a 3-speed motor like this one, or a 3-speed motor that uses only one of its speeds. Locate the wires that go into the furnace motor and cut them as close to the motor as possible which leaves a long piece of wire going back to the control. If your furnace blower motor compartment has a high limit switch, make sure NOT to cut those wires.

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Now that the wires have been cut, it’s time to remove the whole squirrel cage housing. These are usually held in place by two bolts which must first be removed. In this case, the bolts are mounted on top; other furnaces may feature bottom bolts. Use care to ensure that the squirrel cage housing doesn’t fall once you remove the bolts.

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Notice the electrical box just in front of the squirrel cage housing? This will need to be removed first. Your furnace may not have this obstacle.

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Using a flexible drill bit extension equipped with a magnetic nut driver, these top screws are much easier to reach and remove.

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In this case, the electrical box does not need to be fully removed. It is hanging loose where it can easily be pushed out of the way in order to reach and remove the squirrel cage housing.

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Now that the squirrel cage housing has been removed from the furnace and placed on the floor, you can see how dirty this furnace is. In fact, it is filthy!

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Take a look at these photos and look at the excessive debris on the motor’s surfaces and collected within the housing. This is what happens when a furnace isn’t regularly cleaned and serviced. The debris is likely the downfall of this furnace blower motor. The clogged motor could not breathe and it was frequently overheating before it finally quit. Fortunately, the homeowners were home at the time and able to get the motor replaced promptly because the motor stopped working in the middle of an Alaska cold snap. Had the motor not been replaced right away, the entire house could have frozen resulting in burst pipes and cracked toilets! If you’ve ever dealt with water damage from these events, you know that it’s far cheaper to replace furnace filters and have the furnace serviced once per year.

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Removing the motor from the squirrel cage housing involves removing the ground wire and the bolts holding the motor in place.

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Once these items are removed, turn the housing over and find the ¼ inch square nut where the motor shaft protrudes. Loosen the nut and allow the shaft to move. It’s not unusual for the shaft to refuse to budge. If necessary use a liquid wrench or gently tap it out, taking care not to “mushroom” the shaft’s end.

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Flip the housing over again and the motor should slide right out. Notice the old motor’s brackets? You may need to use these same brackets on your new motor as most new motors do not come with mounting brackets. Pay attention to how these brackets are mounted on your old motor before removing them. You may even want to take a digital photo so that you understand how to install them on your new motor.

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If you haven’t purchased a replacement motor at this point, you’ll need to do so. Use the information plate located inside the furnace or the actual motor itself as a guide. Always replace the furnace blower motor with a replacement of the correct size both in terms of horsepower as well as shaft size. Real Plumbing Help used a universal motor capable of clockwise or counterclockwise operation in this replacement.

Inspect your new motor to see if it has oil ports. If so, those must face up in when the replacement blower motor is installed.

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Here’s the original box the universal furnace blower motor came in. The label shows the brand name and horsepower of the motor as well as tells us exactly what capacitor is required. Make sure to replace the capacitor at the same time. The capacitor is not typically included with the motor, so find out the exact type of capacitor needed and purchase one when you purchase the motor.

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Examine the label on the new motor, making sure to read it carefully. Pay close attention as the new motor’s wires may use a different color scheme than your old one used.

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Now, install the mounting brackets onto the new motor, taking care to mount them properly and ensure that the motor’s wires will reach the controller wires that you cut earlier and that the brackets won’t interfere. Clean the squirrel cage housing and then position the motor in its place, making sure that it is centered, can spin freely, and won’t rub. For example, if the motor is too close to one side, it could rub against the housing which causes excessive noise and could damage the motor or the housing.

Once the motor is installed in the squirrel cage housing, connect the wires, reinstall the housing, and remount any other components you may have removed. While you’re at it, don’t forget to replace the filter. After all, you don’t want to have to replace the new furnace blower motor again, do you?

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