Humidity sensing fan wouldn't turn off

Humidity Sensing Fan Wouldn’t Turn Off | Solution From Pros

Sometimes humidity sensing fan wouldn’t turn off. Why? There may be several possible reasons. Power fluctuations, faulty wiring, improper humidistat, or a twisted cork. The reasons are varied. We will only focus on the most potential causes, which are more common and general. Stay tuned!

Before jumping onto the causes of constantly moving humidity fans and the ways to resolve them, let us have some basic knowledge of humidity sensing fans. Afterward, we will discuss the reasons and solutions in detail. Let’s start!

For your convenience, let us first define the humidity-sensing fans,

 “Humidity sensing fans are responsive to the wetness-concentration of the environment”.

When humidity rises to a certain level (60-75%), they automatically turn on, and vice versa-keeping the condensation, mold production, temperature, and fragrance of the environment in control. For your ease, you can say that humidity-sensitive fans keep the environment’s biological, chemical, and physical characteristics in balance.   Humidity-sensing fans used in bathrooms are specifically designed for the bathroom environment only, keeping the humidity level of the bathroom in mind. (Different environments have different physical, chemical, and biological parameters).

There is a built-in humidistat in humidity-sensing bathroom fans, usually set at 60-75%. But you can adjust it according to your bathroom environment. When humidity reaches the limit, the humidistat automatically turns on the humidity-sensing fan to regain the normality of the environment. As a stroke of fate, these humidity-sensing bathroom fans may face impairments. It is a well-known scientific fact that material objects are not eternal. They constantly need human intervention to stay functional. You, by yourself, have experienced such scenarios in your day-to-day life.

Why humidity sensing bathroom fan would not turn off?

We have the necessary information about the humidity-sensing bathroom fans at hand. Now, let us figure out the potential causes of its continuous flow. Remember, whenever you have a problem at hand, try to get all the essential information. Try to look at the issue from all the available perspectives and dimensions before making a genuine and dedicated attempt to fix it. Usually, the solution lies within or near the problem. The causes of the vent fan would not turn off, that is, mechanical ventilation may be varied. To avoid complexity, I will highlight the most critical causes of bathroom fans not removing humidity.

Power fluctuation

The variation and fluctuation in your AC/DC and voltage can be a cause behind the continuous flow of your humidity-sensing bathroom fan. The origin of the disturbance may reside in the power source. But, remember, “Power is always essential. Without power, nothing can be done.”

You can only run a fan with a power source. But, the intensity of the power is a genuine concern.

humidity sensing bathroom fan with light

It would help if you tried to figure out whether the intensity of your power is acceptable for your humidity-sensing bathroom fan or not. If not, try to change the intensity of your power. But, again, there will be an issue! Sudden and instant power fluctuations are not advisable. Take your time. Change always requires time to manifest itself in the upcoming future!

humidity sensing bathroom fan switch

So, analyze and examine your power source; it might be a potential cause of the disturbance. The advisable electric service supply voltage to the humidity sensing fan is AC 120V, 60Hz. 

Improper wiring

Again, if the power source is all right, then the problem may reside in the networking of the power. The wiring structure may stop to turn off the automatic bathroom fan. Examine the installation of your wiring. Re-evaluate it.

humidity sensing bathroom fan

Pulled cord

Your humidity-sensing bathroom fan may have a cord. It may be displaced to a point where the humidistat of your humidity-sensing bathroom fan can become irresponsive and insensitive to the humidity change in the environment.  Resultantly, your bathroom fan not removing humidity.

humidity sensing bathroom fan switch

Pull your cord back to the standard sensor mode, so it may again become sensitive to the wetness-concentration of the environment.

Faulty humidistat

The humidistat is the CPU of your humidity-sensing bathroom fan. For your ease, you can take a humidistat as a humidity sensor. There is often a range of humidity in the settings of your humidistat. Adjust the bathroom fan humidity sensor setting. Wait for the result!

Faulty switch

The switch of your humidity-sensing bathroom fan may have troubles. If you hear a noise while pushing the liver of your switch, then your problem resides in your switch. The sound can be cracking, snapping, and popping. Whenever you notice noise while using your switch, try to fix your switch.

How to fix humidity sensing bathroom fan that would not turn off

The fixing strategy would be different for different causes. If the reason for the continuous flow of your humidity-sensing bathroom fan is power fluctuations, then we will use other methods and so on. We will use different solving mechanics in case of different causes.

Fixing the issue of power fluctuation

  • Use a static var compensator (SVC) which helps reduce the voltage fluctuations.
  • Distribute many smaller capacitor banks throughout the system to strengthen the network’s reactive power compensation.
  • Reconnect the load at a higher voltage level.

Solving the issue of wiring

  • Turn off the power supply
  • Use a voltage tester to check whether it is safe to touch.
  • Mark the wires which go to the humidity-sensing bathroom fan by checking your switch box.
  • Remove your bathroom fan.
  • Pull off your humidity-sensing bathroom fan by revisiting the switch box.
  • Measure the length of your old wire and cut your new 14 gauge wire to size.
  • Initiate your new wiring from your switch to the ceiling.
  • Connect your new wiring with your switch in one hand and with your fan in the other.

Solving the issue of pulled cards

Fixing the problem of the pulled card is relatively easy. I have shared the solution while discussing this problem above in part 3. You can revisit it. For your convenience sake, let me restate it here. Examine your cord and figure out the standard point. Replace it to that point. Isn’t it easy?

Solving the problem of humidistat

For resolving the issue of the humidity sensor, check the settings of the humidistat. Adjust the humidity level according to your environment. Usually, it is kept between 60-75%.

Repairing the faulty switch

  • Turn off the power supply.
  • After removing the cover plate, use a voltage tester to check the voltage supply to see if it is stopped.
  • Remove the top and bottom switches to disconnect your old switch.
  • Check for a broken or loose wire.
  • Remove the wire by unscrewing the terminal screw about one-fourth of the inch and releasing the wire.
  • Cut the above faulty portion of the wire.
  • Reinsert the wire in the switch and reinsert the screws.
  • Now, turn on the power supply and check out the functioning of the switch.

How to reset the humidity-sensing bathroom fan?

So far, we have discussed the potential causes of humidity-sensing bathroom fan continuous movement. Now, let’s try to fix it. For this purpose, we need the necessary apparatus.

  • Voltage tester
  • A wire of 14 Gauge
  • Crimpling tool
  • Cutters for wires
  • Screwdriver
  • Needle Nose Pliers
  • Electrical tape
  • Fixing the humidity-sensing bathroom fan


  • Constantly check the functioning of your humidity-sensing bathroom fan.
  • Try to make your bathroom environment fresh by ventilating the air.
  • Check the intensity of your power supply. Try the intensity of your supplied power in a tolerable range.
  • Use the switch gently. Please don’t be harsh on it.
  • Keep the settings of the humidistats up-to-date.

Frequently Asked Questions

Are humidity-sensing bathroom fans worth it?

Yes. The humidity-sensing bathroom fans are more critical for you than you think. Humidity sensing fan keeps the humidity level, mold production, fragrance, and the environment’s temperature balanced. What?

Let me elaborate on it:

  • Humidity-sensing bathroom fans keep the humidity level in control and ultimately balance the temperature.
  • They also make the fragrance of the environment pleasant.
  • The primary biological function of the humidity-sensing bathroom fan is balancing the mold production rate.

A mold is a structure of fungi. Not all; only a small number of fungi can form molds. The color of the mold is due to spore formation, which contains secondary metabolites. On average, a mold requires 24-48 hours to germinate. But, the mold culture will only be visible after 18-21 days. The colonization process was done long before the visual appearance of the mold culture. Breathing in mold saturated environment can lead to severe allergic and respiratory problems. Humidity fans safeguard us against such issues. In this way, these fans maintain the physical, chemical and biological composition of the environment.

Is a dehumidifier better than a fan?

Yes, a dehumidifier is much better than a fan. It keeps the surrounding environment’s natural, physical and chemical parameters in balance.

How does a bathroom exhaust fan with a humidity sensor work?

The humidity-sensing bathroom fans work by sensing the wetness-concentration of the environment. Whenever the humidity level reaches a certain point, it starts moving to regain the average humidity trim level. Similarly, the humidity-sensing bathroom fan will remain off when the humidity level is below a particular level.

Is it wrong to leave your bathroom fan on?

Yes, it is terrible to leave your bathroom fan on. Why?

The constantly running bathroom fan will decrease the environmental humidity level and ultimately alters the chemical and physical balance of the surrounding environment. It will also affect the rate of mold growth.


In this article, we have discussed in detail what is a humidity sensing fan- a fan sensitive to humidity. Afterward, we discussed the potential causes of why humidity-sensing bathroom fan wouldn’t turn off, and at last, we discussed some practical steps to solve the problem. Could you follow the steps to fix the problem?  If you have anything to add or want to differ on any point, please feel free to reach us in the comment box.



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