Bathroom Fan Humidity Sensor Not Working – Why And What To Do?

If you have an old bathroom fan that doesn't function well, you should consider purchasing a new one. However, if it is far from being old, for example, the humidity sensor is not working, you should try some troubleshooting first. To know why this happens and what to do about it, we conducted thorough research on the internet.

Most likely, the wiring is to blame if your bathroom fan's humidity sensor or timer does not operate. To fix it, switch the power off at the service panel. Attach the wires in their designated slots, and you have to fasten them securely.

We all know that aside from the humidity sensor, there are still some components of a bathroom fan that experience malfunction and damage. Please keep adding if you want to know them all. We will also provide you with the solutions to make your bathroom fan work fine once more.

shower room ventilator, Bathroom Fan Humidity Sensor Not Working - Why And What To Do?

What To Do To A Faulty Humidity Sensor

If you have already checked the wiring of the humidity sensor and it is perfectly fine, there is nothing else you can do but buy a new sensor.

Replacing exhaust fan on bathroom

Fortunately, a brand-new one only costs around $30 these days. Additionally, if your fan came with a humidity sensor when you purchased it, you can freely use its warranty to get a new one.

Check out this humidity sensing fan on Amazon.

Why A Bathroom Fan Is Not Properly Working

Bathroom Design by Interior Designers Bathroom with mirror, sink, water heater

In this section, we will provide details about some of the common issues a bathroom fan experiences, together with their respective solutions.

1. Improper Fan Installation

Unfortunately, the bathroom fan won't work even with the slightest wrong step you might execute in the installation process. So, as much as possible, install every fan component correctly and cautiously.

One of the essential things that you should install is the exhaust duct. Correctly attaching it to the fan is a must because if not, water-saturated air won't be able to escape the bathroom. And that means the bathroom will not have proper ventilation, causing all types of problems.

Additionally, your bathroom fan will experience more malfunctions when any of the other vital parts fail in installation.


Switch the fan off the service panel to freely examine the entire fan. Ensure the following:

  • Correct power plug-in of the fan
  • Proper fitting of the fan
  • Appropriate fastening of the screws
  • Right attachment of the ducting

A thorough examination of the entire fan is likely to reveal a problem. It might be a minor blunder that you can quickly remedy. It would be best to find and solve the problem of your bathroom fan immediately to avoid wasting time and money on costly repairs.

2. Incorrect Wiring Connection

It is the most challenging and risky portion of the installation. If you make a mistake while wiring a new fan, it might not work at all.

Errors in connecting the switch, sensor, or timer might cause the bathroom fan to malfunction.


At the service panel, switch off the power to the fan. If you don't have any idea about the placement of the wiring, we suggest you refer to the manual or consult a trusted video or website. And please be extra cautious with the wires.

Moreover, if you wired the fan correctly, you can now do the same thing to the switch wiring.

If your new bathroom fan isn't operating despite all of the electrical components functioning properly, it's a good idea to consult an expert.

3. Manufacturing Issue

A bathroom fan might still not work properly even if the installation went well. One primary reason for it is the brand and model. If you purchased a cheaper model, the possibility of the malfunction is higher.

In most cases, it may be because of the small faulty components of your bathroom fan.


If your bathroom fan consists of a damaged or corrupted component, or it doesn't work even if you noticed no damage, it would be best to call the manufacturer's customer support to ask how to replace or return the unit.

However, the immediate solution of a sales representative is to conduct an assessment and a repair. But if the fan is still under warranty, you can request a replacement.

4. The Humidity Sensor or Timer Has Incorrect Program

If you notice that the humidity sensor of your bathroom fan has correctly placed wiring, yet it still doesn't work, you may want to check or modify its programming. The humidity sensor's programming is sometimes the root of the errors. This issue can make the bathroom fan operate more frequently or not frequently enough.

As EPA suggests, it would be best to maintain the humidity below 60%. If the humidity level in your home is usually more significant, modify the sensor and make it higher so that the bathroom fan will only turn on when the humidity is way too high.


Switch the bathroom fan off from the service panel. Once you finish, detach the grill and find the timer or humidistat so that you can calibrate both of them. To maximize the fan's efficiency, change the time or the humidity level at which it should turn on.

5. Tripped Circuit Breaker or Blown Fuse

A construction worker is installing, replacing a bathroom exhaust, ventilation fan to remove moister and od

Aside from the wiring, another electrical factor that can affect the functionality of your bathroom fan is the fuse or circuit breaker.

This issue is largely clear if additional electrical devices attached to the same fuse are also not working.

However, suppose the bathroom fan is the lone electrical device that isn't working. In that case, you can determine whether or not the issue is with your circuit breakers by inspecting them and checking for blown fuses, red or orange lights adjacent to that particular breaker, or switches that are off or in strange places.


The tripping of circuit breakers or blowing fuses may be because of various issues, including an overloaded circuit, short-circuiting, a faulty motor,  or the wrong installation of a fuse.


Investigate the surroundings to look for any signs of humidity that could have led to the electrical short-circuit. But if you can't find any moisture, we suggest you look for broken wiring. If either the appliance itself or the wiring sustains damage, it is imperative to contact an electrician.

Defective Motor

Repair, or better yet, replace the fan motor.

Overloaded Circuit

Be sure to remove any electronics or home appliances from the overloaded circuit. Check that the connections for each circuit are consistent throughout the board.

Incorrect Fuses

It would be best to investigate before replacing the erroneous fuse with the correct one, in which you should use the appropriate amperage rating.

6. Stuck Damper

You'll know that your bathroom fan has problems with dampers if it works at a sluggish pace having inadequate airflow. 

You can find the dampers at each rear of the fan's exhaust duct. The airflow will be feeble if either of them does not correctly open because air cannot flow as readily via the ducts.


Since the inner damper is seldom an issue, it would be best to begin the repair with the external damper. Good thing that you can move it by hand. This damper is to blame if it doesn't open or close smoothly. Additionally, you can utilize a tissue to check the airflow. You'll know that the airflow is inadequate or too feeble if it doesn't flutter.

Moreover, repair the external dampers by only lubricating them, cleaning around them, and clearing out blockages around them.

On the other hand, there is an issue with the internal damper if the outer damper is working properly. To fix it, take off the grill and use your finger to feel the damper. The damper should be able to move freely after applying lubrication to its hinges and moving it inwards and outwards.

7. Too Airtight Bathroom

Renovated bathroom with toilet, shower tub, and sink

If you don't find any issue, just as we have mentioned from numbers 1-6, your bathroom might be the root of the problem.

Replacing the air inside your bathroom is necessary. When the new air replaces the old stale air, the pressure gradients ensure it moves through the duct more easily.

If you can't obtain fresh air in your bathroom efficiently, it's because it's probably too airtight.


Check the distance between the bathroom door and the floor; you must ensure that it is at least 1/2-inch high. As a result, this space can introduce fresh air inside your bathroom. 

You can straightforwardly replace the air inside the bathroom by opening a door or having space at the bottom of the door. Furthermore, it's best to do this with the bathroom fan because it helps circulate the air.

Check out this bathroom ventilation fan on Amazon.

What Is The Recommended Duration Of Bathroom Fan Ventilation

For a bathroom to have sufficient ventilation, the Home Ventilation Institute (HVI) recommends that it go through around eight air changes every hour. To ensure the removal of all moisture in the bathroom after a shower, the HVI also suggests making a minimum of three air changes or turning on the bathroom fan for 20 minutes.

Wrap It All Up

shower room ventilator

In a bathroom fan, it is not only the humidity sensor that cannot function well. Several bathroom fan components don't work properly, too. However, it would be best to try a DIY repair before buying a new one or calling an HVAC professional. 

We hope you enjoyed reading. If you wish to continue, you can check these posts out!

Bathroom Vent Fan Dripping Water – What To Do?

How To Insulate A Bathroom Exhaust Fan

What Should The Humidity In My House Be?

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