Why Does Your Bathroom Fan Rattle? 5 Causes and Fixes

Giovanni Valle is a licensed architect and LEED-accredited professional and is certified by the National Council of Architectural Registration Boards (NCARB). He is the author and managing editor of various digital publications, including BuilderSpace, Your Own Architect, and Interiors Place.

Affiliate Disclaimer: Some of the links below are affiliate links. As an Amazon Associate, I earn from qualifying purchases.

Bathroom fans are infamous for being noisy, but if yours is humming, rattling, or knocking, there is probably something wrong with it. As long as you know how to identify and fix the problem, keeping your fan quiet is a simple task that anyone can do!

Here are some things that could cause a noisy bathroom fan:

An old motor
A motor that vibrates a lot
Blocked or misaligned fan blades
Narrow air ducts
Loose mounting equipment

Let’s talk about each of these components that might be making your bathroom vent rattle so that you can diagnose your fan’s issue. I’ll also discuss how to fix any of these problems so that your bathroom can be a peaceful place again.

1. An Old Motor

If you hear a humming sound coming from your vent, the problem likely has something to do with your fan’s motor.

The instrument that spins the fan blades in your vent is the motor.

Since bathroom fans are exposed to tons of dust, moisture, and other debris, their motors are prone to clogs, water damage, and fungal growth. As the engine gets older, it gets weaker and less efficient. If you leave too much gunk on it, the motor will die completely.

The humming sound that the motor makes happens because it is experiencing too much resistance. Naturally, as a motor gets older, it can’t spin as quickly as it used to, making a sound like a tiny revving engine.

It is essential to fix motor issues since they could break the entire fan if left for too long.

How To Fix an Old Bathroom Fan Motor

Although an old motor will eventually need to be replaced, you can clean and lubricate your existing motor to keep it running sound-free and extend its life.

You will need a rag, a small brush like an old toothbrush or microfiber cloth, and a spray-can of WD-40 (available on Amazon.com) to lubricate and clean your fan.

To clean and lubricate the motor:

Turn your fan off.
Remove the fan cover.
Use a damp rag to clean off superficial dust, mildew, and other debris.
Use an old toothbrush, microfiber cloth, or brush to clean the fine details of the motor, fan blades, and fan casing.
Apply a generous coat of WD-40 to the motor and fan blades, paying close attention to the joints between the fan and the motor.
Replace the fan cover.
Turn on your fan to see if the sound is better.

If the sound has not improved, you may have another issue with your bathroom fan, or the motor may be so old that it cannot run smoothly. Try some of these other tips and tricks before replacing your vent, but if all else fails, you may need to call a maintenance specialist or buy yourself a new fan.

2. A Motor That Vibrates a Lot

If you hear a humming, clanging, or ringing sound from your bathroom fan, your motor might just be vibrating too much.

Depending on the setup you have, your motor could cause extra noise. Usually, noisy motors can become a nuisance if they are in direct contact with metal or are too high-powered for the fan you own.

That’s because motors inherently vibrate when they conduct enough power to spin fan blades. If your fan’s motor intensely vibrates against metal or other hard, noisy materials, you will surely hear it.

How To Fix a Motor That Vibrates a Lot

If your motor is noisy because it vibrates too much, you can use Sorbothane rubber to absorb the noise.

Rubber will provide your motor a bumper that absorbs shock, keeping the fan’s natural vibration from clanging against other noisy materials. In addition, Sorbothane rubber is one of the best soundproofing materials on the market, so using it on your fan can make your bathroom a quiet, tranquil place again.

If you can, you should purchase Sorbothane rubber that has an adhesive backing, like Isolate It!’s Sorbothane rubber sheets (available on Amazon.com).

To fix a motor that vibrates a lot:

Turn off your fan.
Remove the outer cover.
Wipe your fan and its mounting with a damp rag to ensure that the adhesive can stick.
Cut your Sorbothane rubber into small strips of around 1 inch (2.54 cm) wide.
Stick your Sorbothane rubber to the vent around the motor, ensuring that you do not block the fan’s blades.
Turn your fan on to ensure that the rubber strips do not inhibit it.
Replace the fan’s cover and enjoy the silence!

3. Blocked or Misaligned Fan Blades

If you hear a clanging, rattling sound from your bathroom fan, you might have a dirty vent.

Because bathrooms are so humid, dust, hair, and dirt can quickly get stuck to the fan’s blades and the cover, blocking the spinning motion. When that happens, your bathroom vent will make more noise than usual since the fan blades will hit the debris trapped in the cover.

In addition, if your fan blades are misaligned, they may hit the casing or wires inside your bathroom vent, making a knocking sound.

How To Fix Blocked or Misaligned Fan Blades

Luckily, fixing fan blade issues is very simple, so don’t be afraid to do it yourself.

To unblock and align your fan blades:

Turn off your bathroom fan.
Remove the outer cover from the vent.
Use white vinegar or warm water and a rag to clean the fan cover.
Wipe down the fan blades with a damp rag or toothbrush.
Spin the fan blades with your finger while wiping the axel that connects your fan to the motor.
If the fan blades are crooked or bent, slide them back into place, ensuring that the blade mechanisms are still in good shape.
Ensure that the entire fan is free of debris, then replace the cover.

4. Narrow Air Ducts

If you have narrow air ducts, you may hear a whooshing, banging, or buzzing sound.

When your fan is on, it pushes air up through metal ducts to remove it from your home. If the vent is narrow, it often makes more noise.

That’s because when the air rushes through a narrow duct, the pressure is higher than if the duct were wider. For example, narrow ducts are similar to the difference between whistling and normal breathing. To whistle, you need to close your mouth and purse your lips, but when you are breathing, your mouth is open.

So, just like when you whistle, a narrow duct will make more noise than a larger one.

Most bathroom fans that are designed to be silent use a 6-inch (15.24-cm) duct, while many older and cheaper models use a three- or four-inch (7.62- or 10.15-cm) duct.

How To Fix Narrow Ductwork

If your ductwork is narrow, you can still buy an adapter like Hon&Guan’s Straight Duct Increaser and Reducer (available on Amazon). These adapters are excellent for bathroom fans and are also extremely easy to install.

In addition, you may need some duct tape to seal the tubing. I recommend AmazonCommercials Standard Duct Tape (available on Amazon.com). You can get it in a pack of three since you never know when you’ll need some duct tape!

To install a duct adapter on your bathroom fan:

Turn off your fan.
Go to your attic or wherever you can access your fan duct from above.
Unplug the duct tubing from your bathroom fan.
Plug your adaptor’s small end into your bathroom fan’s duct outlet.
Plug the duct tubing into the other end of your adaptor.
Optionally, you can seal the tubing with duct tape.

5. Loose Mounting Equipment

When your fan makes a vibrating or rattling sound, the mounting equipment may be too loose, or it may be broken.

Since fans vibrate while running, they usually have brackets, screws, and clips that keep the motor and fan blades from making too much noise.

So, if the mounting equipment is loose, your vent fan will probably make more noise and a clanging sound.

How To Fix a Bathroom Fan With Loose Mounting Equipment

Before going in with the screwdriver, you can quickly check to see if loose mounting equipment is your problem. To check, remove the outer cover and try to shake the fan. If it wriggles around, then you have found the issue!

To tighten loose mounting equipment:

Keep the fan off and remove the cover.
Use a screwdriver to tighten the screws around the motor, near the fan blades, and on your fan’s inner panel.
Turn on the fan to see if the sound improves and replace the cover.

If your fan’s noisiness does not improve, you may have another issue like undersized ductwork or a misaligned fan blade.

Final Thoughts

So, all in all, there are several reasons your fan might be noisy, including an old or vibrating motor, dirty or misaligned fan blades, a narrow duct, or loose mounting equipment. Fixing all of these things is simple, so if one method doesn’t do the trick for you, you can always try another one to identify the problem.