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Bathroom Fan Starts Slowly: Why and How to Fix It

You have just taken a bath or shower. Now it’s time to kick on the bathroom exhaust fan and let it do its job.

But after flipping the switch, the fan seems to take forever to turn on. All the while, moisture is seeping into the walls and floors of your bathroom. 

There are many reasons why a bathroom fan may start slowly from a bad switch, a damper that’s frozen shut, or your fan’s manufacturer included a delayed start system. Once you figure out why your fan is starting slowly, the issue is usually easy to resolve.

It’s vital you find out what is causing your fan to start slowly and fix the problem as soon as you can before mold or water damage finds a footing in your bathroom.

dirty bathroom fan

Why Do Bathroom Fans Start Slowly?

Delayed Start

Some fan manufacturers included a delayed start system, such as the Panasonic bathroom fan delay start.

These delay systems are usually installed to save electricity or allow sensors to determine if there is enough moisture to justify the operation of the fan.

However, most fans do not have a delayed start system, so it’s best to check whether your fan has one or not.

Debris or No Lubrication

Bathroom fans are usually neglected when it comes to cleaning and maintenance.

All this dust and debris can build up in your fan blades, making it hard for them to turn.

Another maintenance issue is the bushings that allow your fan blades to spin haven’t been lubricated in many years resulting in a slow start.

Bad Switch

Sometimes, the switch turning your fan on and off might be old, faulty, or not working properly.

If you hear a humming noise after you flip your switch on, yet your fan is not moving is often a sign that your switch has gone bad.

Frozen Damper

Extremely cold weather can freeze your damper while it is still open.

The damper allows air brought in by your fan to exit your bathroom and then closes to stop cold air from entering your bathroom.

If your damper remains open, this cold air can affect your fan’s motor making it so your fan has a hard time starting up.

If you have a frozen damper, you usually just have to wait for the weather to warm up or try and manually close the damper.

How to Fix a Bathroom Fan That Is Taking a While to Start

Adjusting a Delayed Start System

First, your bathroom fan should have a manufacturer and model number imprinted somewhere on the fan.

Use that information to determine if your fan has a delayed start system.

If it does, you can contact the manufacturer or consult the manual that came with the fan for the exact method to adjust the delayed start.

Lubricating and Removing Debris

To clean your fan, simply remove the cover and unscrew the fan from the ceiling.

It’s recommended you wear a dust mask and eye protection to prevent the dust from getting into your eyes and lungs.

With your fan removed, you can use a cloth and a small brush like a toothbrush to thoroughly clean your fan, then apply a few drops of lubricating oil to the bushings and shaft.

You can contact the manufacturer to find the best lubricating oil for your fan. Then, wait for the oil to dry before reinstalling your fan.

Replacing a Bad Switch

If you have determined that your fan’s switch is the cause of your issues, this switch can be easily replaced.

Its recommended that you shut off all power running to the bathroom to avoid any electrical hazards.

Removing your old switch usually requires the removal of a few screws and wires.

If you feel uncomfortable working around electricity, you can hire a professional to replace the switch for you.

Adam McCoy

Adam is an HVAC expert and the owner of Mackydo's HVAC Services with decades of experience in fixing and installing air conditioning units, furnaces, and every type of cooling and heating equipment you can think of.

Adam believes that your home is your sanctuary. He loves sharing advice based on his lifelong experience and treats every HVAC problem as if it was his own.

About Loo Academy

At Loo Academy, our mission is to offer trusted advice for everything related to bathrooms (design ideas, plumbing advice, showering & bathing tips, remodeling guides, and more) — a place where we all spend a great deal of time.

We work closely with qualified experts and follow a thorough editing and fact-checking process before publishing content.

Published content is regularly fact-checked and revised so that the information we provide is accurate and up-to-date.

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