8 Reasons Why a New Bath Fan Is Not Working (List With Solutions)

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If your old bathroom fan isn’t working properly, it is easy to just replace it with a new one. However, when the defective bath fan is brand new, replacing it is not the first step most would like to take. To avoid having to purchase another brand new bath fan, read on for troubleshooting and reasons for malfunctioning that could save you effort, time, and money.

1. Faulty Unit Installation

Unfortunately, it is very easy to incorrectly install a bath fan unit. Any step that goes wrong can lead to the bathroom fan not running at all. 

If the fan motor is not installed properly, it will not function and the fan cannot do its job.

If the exhaust duct is not attached to the fan, water-saturated air cannot exit the bathroom properly and the bathroom will not be ventilated well or at all, which leads to all sorts of problems.

If any of the other essential components of the bathroom fan aren’t in working order, it is likely that the whole unit will not function properly. 


Make sure the power to the fan is turned off at the service panel and then investigate the whole of the unit. Are all screws screwed tight? Is the ducting attached properly? Does the unit fit correctly into where it was installed? Is the power plugged in correctly?

An extensive check of the whole fan will most likely show a problem with the unit. It could be an easy mistake and therefore a simple fix. If a problem is found and solved, your new bathroom fan can be fixed without much hassle or any money spent. 

2. Wiring Is Connected Incorrectly

Wiring can easily be the most difficult and dangerous part of the installation. These aspects of wiring can result in mistakes that lead to an entirely new fan not functioning. 

Not only is the wiring inside of the fan itself subject to error, but an error in wiring the switch, sensor, or timer can also cause a failure in the functioning of the bathroom fan.


Make sure the power to the fan is turned off at the service panel. While consulting your manual or a trusted site or video, check that all wires are connected properly and screwed in tightly. Ensure that the wires are not damaged in any way.

If the fan unit seems to pass the test, assess the switch wiring in the same way you did the unit wiring (properly connected, tight, not damaged).

If all components of the wiring seem to be in working order, and you are positive that the reason your new bathroom fan is not working is because of the wiring, it is advisable to seek an expert’s opinion. 

Whether this is a trusted friend or family member or a licensed electrician, it is always good to get a second opinion. 

3. Fan Manufacturer Fault

Even if the fan is installed perfectly and the wiring is beautiful, a bathroom fan can still malfunction. Nobody is perfect and if your fan is not operating, especially if it is a cheaper model, it could be the result of a manufacturer fault. 

Like most machines, a fan has many small parts that contribute to its whole. If the whole is not working, it is possible that this is due to any of the small mechanisms of the bathroom fans being faulty. 


If you notice a broken or warped component of the fan, or even if you can just find no other reason why the fan would not be working, it is definitely recommended to contact the manufacturer. Consult the manual for options relating to a return or assessment of your bathroom fan unit. 

A conversation with a sales representative would most likely consist of how to fix the problem with as little cost as possible. 

Whether the whole unit must be replaced or a small component replaced would be up to your observations and/or the associate sent to assess the unit.  

However, as the fan is new, it should still be within the warranty period and most manufacturers will simply replace your unit with a new one.  

4. Defective Humidity Sensor or Timer

If your bathroom fan isn’t activated with a switch, you more than likely have a humidity sensor or a timer.

A humidity sensor or timer defect could mean that the bathroom fan isn’t turning on at all, not turning on when it should, or is on all the time. None of these situations are ideal.

A humidity sensor or timer is often installed where a switch would usually be for that bath fan. If a sensor or timer isn’t working, the problem is most likely with the wiring. 

Read my article on why bathroom fans keep running for more information on how a defective humidity sensor can cause problems with a new fan.


Make sure the power to the fan is turned off at the service panel. Make certain that the wires are connected properly in their allotted slot and that they are screwed in tightly. If the wiring is in good order, there must be another problem. 

There isn’t much else you can do for a defective sensor or timer whose wiring is correct other than purchase a new one. Thankfully, a brand new one is only about $30. Alternatively, if your fan came with a humidity sensor or timer, you can return it under the warranty and get a new unit.

5. Incorrectly Programmed Humidity Sensor or Timer

If you know the root of the problem is the humidity sensor or timer, the issue might not be the defectiveness of the device, but an error in programming.

Issues with an incorrectly programmed humidity sensor or timer will result in a bathroom fan still running and doing its job, but not for long enough, running more often than it needs to, or not running for long enough to dispel humidity quickly.

If the humidity sensor is programmed at too high or low of a humidity percentage, the bath fan will run too often or not often enough. A good humidity level to set your humidity sensor at is about 30-50 percent. 

If your humidity level is naturally higher than this, set it higher so that your fan operates only when the bathroom is far too humid.

As far as an incorrectly programmed timer, if the set time is too much or too little, it must be adjusted in order to operate for the optimal time (at least 20 minutes after your shower).


Make sure the power to the fan is turned off at the service panel. You can then remove the grill and locate the humidistat for sensor calibration, or timer for timer calibration. Adjust either the humidity that the fan should activate at or the time so that the fan is as efficient as possible.

6. Fuse Blown/Circuit Breaker Tripped

If wiring is done properly, a defective bathroom fan can still be negatively affected by electrical problems. In this case, it would be the fault of a circuit breaker or fuse.

This problem is especially obvious if other electrical appliances connected to the same fuse are also not functional. 

If your bathroom fan is the only electrical appliance not functional, you can confirm or deny that it is a circuit breaker problem by assessing your circuit breaker and looking for a blown fuse, a red or orange light next to that specific breaker, or a switch that is off or in an odd position.


Short-circuiting, a defective motor, an overloaded circuit, and the incorrect installation of a fuse can all cause circuit breakers to trip or fuses to blow.


Search the area for dampness that may have caused the short-circuiting. If dampness cannot be found, look for damaged wiring. Whether there is damage to the appliance or the wiring, an electrician must be called. 

Defective Motor

This fix is fairly simple: replace or repair the fan motor.

Overloaded Circuit

Make sure to relocate devices or appliances from the overloaded circuit. Make sure each circuit’s connections are even across the board.

Incorrect Fuses

Do your research and replace the incorrect fuse with the correct fuse with the right amperage rating.

7. Damper Is Stuck

If your new bathroom fan operates but at a slow rate with weak airflow, problems with one or more dampers might be the issue.

Dampers are located at each end of the exhaust duct of a bathroom fan. If either one is not opening properly, airflow will be weak due to air not being able to flow as freely through the openings (entering the ducts or exiting the ducts). 


Start with the exterior damper since the interior one is rarely a problem. Move the damper by hand. If it sticks or does not open with ease, this damper is your problem. You can also test the airflow with a tissue If the tissue doesn’t flutter, the airflow is too weak.

An exterior damper can be fixed by lubricating its hinges, cleaning around the damper, and clearing any obstructions around the damper or in the ducts. 

If the exterior damper is operating without issue, the interior damper is the problem. Remove the grill and test this damper with your finger. If it is not moving readily, apply lubricant on its hinges and move the damper back and forth until it moves without issue. 

8. Bathroom Is Too Airtight

If your dampers are working properly and your airflow is still weak, your problem might not even be with the appliance or its ducting, but with the bathroom itself. 

With operational dampers, ductwork, and a bathroom fan, air from the bathroom is carried through the ductwork and released outside. The air in the bathroom must still be replaced, though. This replacement air ensures the pressure gradients facilitate movement of the “old” air through the duct.

If replacement air cannot be easily acquired, it is most likely because the bathroom is too airtight.

An airtight bathroom can also result in a sewer smell when running the bathroom fan.


Make sure the space between the bathroom door and the floor is at least half an inch high. This way, air from the rest of the house can enter the bathroom. 

Along with space at the bottom of a door, opening a door is great for speedy air replacement. It is an especially good idea to do this while the bathroom fan is running. 










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