AirKing Lasko B-Air Blue-dri

My Exhaust Fan Isn’t Working Properly

A question we get on a regular basis is people telling us their exhaust fan isn’t working properly. It is a simple enough question but it has a multitude of answers. While it is impossible to list every scenario, we will look at some more common issues that happen with exhaust fans no matter who the manufacturer is. Generally when an exhaust fan isn’t working properly it can be classified into one of two categories – mechanical or installation.

Mechanical issues generally occur over time and are affected by a host of factors such as usage, environmental issues (living near salt water), where the unit is located and so forth. Some issues that might seem like they are mechanical could actually be installation issues and we will get into those in the next section. Generally if the fan does not operate right after installation it is most likely an installation issue rather than a mechanical one – not always but most of the time. Some of the common mechanical issues are:

The fan stops operating.

This could be the motor has worn out and has stopped running. You can expect this in older fans that have been operating for a long time. If it is a newer fan, check your warranty as many fans have at least a one-year warranty and some up to a 5 year warranty.

Fan starts making loud noises – “metal” sounds.

More than likely this is because something inside or around the fan has come loose. This could be something in the mounting system, a weld on the housing, the motor mount has come loose and so on. If it is the mounting, simply tightening the mounting screws or re-enforcing the connections to the joist or stud should solve it. If the welds on the housing have come undone this is a little harder to fix and you might be better off replacing the unit – especially if it is an older unit.

Fan starts making loud noises – “rattling” sounds.

This is typically attributed to the fan blade becoming out of balance and can sometime sound like the fan is pulsing. This happens in one of two ways. The first is the blade becomes warped. This can happen if there is excess heat or chemicals. A more common reason for this is the fan blade my be dirty and have a build-up on it causing it to be out of balance. Refer to your unit’s instructions sheets for care and maintenance. The good news is this is usually a fairly simple fix.

Doesn’t seem as if the fan is moving the same amount of air as it used to.

If the amount of air being moved decreases over time or the sound of the fan increases over time, the main culprit is usually a build up in the ducting or a blockage at either the wall or roof cap. Bird’s nests are a common issue. Check to see if there is anything blocking where the fan is exhausting.

If you determine it is not a mechanical issue, then the reason your exhaust fan isn’t working could be an installation issue. In general you should notice these issues right away but there are some that will show up a little later. Some of the common installation issues are:

Fan does not turn on.

This is usually a wiring issue where they were not connected properly. Check the wiring diagram in your installation instructions. Another common issue is that sometimes people forget to restore power to the unit either at the circuit board or at the wall switch (don’t worry, it happens to the best of us).

Fan does not operated as expected.

Here is where it gets a little more difficult to pinpoint the issue and it requires a bit of investigative work. First, check to see if the size of the duct collar on the unit matches the duct size you are connecting to. If the duct you are connecting to is smaller, you will loose airflow (CFM) and increase sound (sones). Going from smaller to larger ducting is fine but reducing it can cause some issues. Second, determine how long and how many turns the ducting has before the air leaves the home. The longer the ducting and the more turns it makes, the more static pressure the air has to overcome. This will cause the fan to work harder, reduce the airflow and in many cases increase the sound. A best practice is to keep the ducting as short and straight as possible. Third is what type of ducting is being used. It is always recommended that straight, ridged ducting be used. While flexible ducting is easier to use, it can decrease the performance of the fan – especially if it has a bunch of turns and twist like was mention above. Sometimes these items can’t be avoided. If you can identify them in the planning phase however, you might be able to address them there by using a higher power and quieter fan to compensate for the performance “lose” you might experience.

Fan makes loud or rattling sounds immediately after installation.

We touched on a few of these items above, but if they are happening immediately after installation it probably has to do with how the fan was installed. With the power OFF, check to make sure the fan’s housing is securely fastened to the joist or stud. Next check to see if the fan blade is out of balance or is hitting the housing as it spins (you can spin it with your hand). Check the duct collar and connections to make sure they are all secure. Check the motor mount. Many fans have what is called a venturi or a venturi plate that holds the motor in place within the housing. If this is not installed properly or securely it might rattle or cause the fan to be out of balance.

Identifying why your exhaust fan isn’t working properly can sometimes be a tricky but utilizing the suggestion we laid out in this post will hopefully help. For more information about exhaust fans, utilize the tabs at the top of the page. If you are looking for a specific Air King model, utilize the search feature or access instruction and user manuals here.

Arrow Up