The NuTone 672RB motor is a compact but vitally important component found in many older residential ventilation and exhaust systems, particularly bath fans, ceiling heaters, and combination units that were widely installed from the 1960s through the 1990s. If you own a home with a vintage NuTone fixture and it has suddenly gone silent, started rattling, or stopped moving air altogether, there is a very good chance the motor is the culprit. This relatively small electric motor sits at the heart of the unit, driving the fan blade that pulls humid air, odors, and airborne contaminants out of your bathroom or utility space.
Understanding what this motor does, how to diagnose its failures, and how to replace it correctly can save you the expense of ripping out an entire fixture and installing a modern unit. Many homeowners are surprised to learn that the NuTone 672RB motor is still available through specialty parts retailers, making a straightforward repair both affordable and surprisingly practical. This article walks through everything from identification and troubleshooting to replacement and long-term maintenance.
What the NuTone 672RB Motor Actually Is
The NuTone 672RB is a small shaded-pole or permanent split capacitor electric motor designed specifically to drive the blower wheel inside NuTone ventilation products. It typically operates on standard household 120-volt AC current and spins at a relatively modest RPM, which is intentional. Ventilation fan motors are engineered for quiet, continuous operation rather than high torque, so they prioritize smooth airflow and low noise over raw power. The 672RB designation refers to a specific frame size, shaft configuration, and mounting pattern that allows it to drop directly into the housings of particular NuTone models.
What makes this motor somewhat distinctive is its mechanical interface. The shaft is sized and positioned so that the fan blade or blower wheel presses onto it at a precise depth, and the motor body is held in place by a mounting bracket or strap assembly inside the fan housing. If you try to substitute a generic motor with a different shaft length or diameter, the blade will not sit correctly, and the unit will vibrate or fail to move air efficiently. That is why matching the exact part number matters far more than simply finding a motor that "looks about right."
Common Applications and Compatible Fixtures
The 672RB motor is most commonly associated with NuTone bath fan and heater combination units, as well as standalone exhaust fans from the same era. These were extremely popular in mid-century and late-twentieth-century American homes because they combined lighting, heating, and ventilation in a single ceiling-mounted housing. Builders favored them for their space efficiency, and millions of these units were installed across suburban housing developments.
Because these fixtures were built to last, the housings themselves often remain in perfectly good condition decades later, while the motor inside has simply worn out from years of spinning. In many cases, the fan blade, grille, light socket, and heater element are all still functional. Replacing just the motor allows you to restore the entire fixture at a fraction of the cost and labor of a full replacement, which is why demand for the 672RB part has persisted long after the original product lines were discontinued.
Recognizing the Symptoms of a Failing Motor
A failing fan motor rarely dies without warning. The most common early symptom is increased noise, often described as a grinding, humming, or rattling sound that was not present when the unit was new. This usually indicates worn bearings, which allow the rotor to shift slightly as it spins. Another early sign is reduced airflow, where the fan still turns but no longer moves enough air to clear steam from a bathroom effectively.
In more advanced failure stages, the motor may fail to start altogether, producing only a low hum or a clicking noise when you flip the switch. This can be caused by a seized bearing, a burned-out winding, or a failed capacitor in capacitor-start variants. In the worst cases, a motor that overheats can trip a thermal overload protector, causing the unit to shut down intermittently and restart only after it cools. If you notice a burning smell, stop using the fixture immediately and disconnect power before investigating further.
Diagnosing and Replacing the Motor Safely
Before you order a replacement, it is worth confirming that the motor itself is the problem rather than the switch, wiring, or a clogged vent duct. A fan that receives no power at all will not hum, so if the unit is completely dead, test the wall switch and the connections inside the housing first. Similarly, if the motor hums but the blade does not spin, the blade may simply be obstructed by debris or have come loose from the shaft.
Once you have confirmed the motor is failing, the replacement process is fairly straightforward for someone comfortable working with basic hand tools. The critical first step is always shutting off power at the circuit breaker, not just the wall switch. Ventilation fans are often on circuits shared with bathroom lighting, so verify with a non-contact voltage tester that the wiring inside the housing is truly de-energized before you touch anything.
Steps for Removing the Old Motor
Removal typically begins by pulling the grille and removing the light lens or heater assembly, which exposes the internal mounting hardware. You then disconnect the motor's electrical leads, noting carefully which wire connects where, and unbolt or unsnap the motor bracket from the housing. In some NuTone models, the entire motor and blower assembly slides out as a single unit, while in others you must separate the fan blade from the shaft first.
Photographing each step before you disassemble anything is one of the smartest habits you can develop for this kind of work. Wiring colors, bracket orientation, and blade depth on the shaft all matter, and a few quick photos on your phone can save you significant frustration during reassembly. If the fan blade is stuck, avoid prying aggressively, since these blades are often made of fragile plastic or stamped metal that bends easily.
Installing the Replacement and Testing It
When the new 672RB motor arrives, compare it side by side with the old one before installation. Check the shaft diameter, shaft length, mounting hole spacing, and wire lead colors. If everything matches, press the fan blade onto the shaft to the same depth as the original, then reattach the motor to its bracket and reconnect the wiring in the same configuration you documented.
After reassembly, restore power and test the unit at the wall switch. Listen for smooth, quiet operation and feel for strong airflow at the grille. If the motor hums without spinning, or if it vibrates significantly, shut it off and recheck the blade seating and bracket alignment. A properly installed motor should run quietly and start immediately without hesitation, restoring the fixture to something close to its original performance.
Longevity, Maintenance, and Smart Alternatives
Getting a replacement motor to last is largely a matter of keeping the surrounding system clean and reducing unnecessary wear. Dust and lint accumulate on fan blades over time, throwing the assembly out of balance and putting extra strain on the bearings. Cleaning the blade and grille once or twice a year is a simple habit that can meaningfully extend motor life.
It also helps to run the fan for a few minutes after a shower rather than switching it off immediately, since this allows residual moisture to clear and reduces corrosion inside the housing. If your home has long or convoluted duct runs, consider whether the fan is working harder than it should be; excessive static pressure is a quiet killer of small motors because it forces them to operate under continuous load.
Repair Versus Full Fixture Replacement
For many homeowners, replacing just the motor is clearly the better financial choice. The motor itself is inexpensive relative to a new fan and heater combination, and the labor involved is measured in an hour or two for someone with basic DIY skills. You also avoid the messy and sometimes costly work of cutting drywall, modifying ceiling openings, and running new wiring for a modern fixture.
That said, there are situations where a full replacement makes more sense. If the housing is rusted through, the heater element is dead, or the unit's wiring insulation is brittle and cracking, investing in a modern ENERGY STAR rated fan may be wiser. Newer units are dramatically quieter, often rated below one sone, and consume less electricity. In those cases, the 672RB motor becomes less of a repair solution and more of a temporary stopgap.
Sourcing Genuine Parts and Avoiding Counterfeits
Because this part has been out of production for years, the market includes both genuine new-old-stock motors and aftermarket equivalents of varying quality. Genuine or high-quality aftermarket motors will specify the correct voltage, amperage, rotation direction, and shaft dimensions, and they usually include clear installation instructions. Beware of listings that provide no specifications at all or that show a generic photo of an unrelated motor.
Reputable appliance and HVAC parts suppliers typically allow returns and provide technical support, which is worth paying a small premium for. You will also want to verify the rotation direction, since a motor that spins the wrong way will push air into the room instead of exhausting it. Checking part numbers against your fixture's model plate before ordering is the single best way to avoid a frustrating return.
If your vintage NuTone fixture still has life left in its housing and wiring, giving it a fresh motor is one of the most satisfying small repairs a homeowner can take on. The part is accessible, the process is forgiving, and the payoff is immediate: a quiet, functional ventilation system that quietly does its job for years to come. Take a few minutes to confirm your model number, order the correct motor, and give that old fan the second wind it deserves.