Attic Fan NOT Working? 7 Common Problems & Troubleshooting Steps

Attic fans require the least maintenance of all home equipment. They run smoothly from your rooftop or gable without needing any supervision. But there are some occasions when they fail to work.

In most cases, the attic fan not working is due to a faulty motor or a faulty thermostat. Troubleshooting the attic fan will help you identify the problem and rectify it.

I must warn you first that in most cases, there is no way to repair a damaged attic fan; you will have to replace either the thermostat or the motor. If you are unlucky, you won’t find a new motor to replace it with, so in the end, you will end up replacing the whole fan. However, if the fan is covered under warranty, the manufacturer will replace the fan for you at no cost.

What happens if an attic fan stops working? If your attic fan stops working, it will reduce the ventilation of your attic. This means that the hot air will be trapped in the attic, causing the house to warm up.

If your attic exhaust fan is not working, feel free to check this list of common problems to find the apt solution;

Attic fan not working? common problems and their solutions

Given below are the most common problems with attic fans;

1. The attic fan not working (Troubleshooting Steps)

Sometimes your attic fan can just stop working, it won’t spin or hum. This can be due to many reasons; the motor could be faulty, the controller could be faulty, the temperature setting may be high or there is something wrong with the electric socket.

Determining the problem, in this case, can take a while. Here’s how to troubleshoot this issue;

Check thermostat setting

The first thing to do here is to check the temperature setting of the fan’s thermostat. The fan won’t run if the temperature setting is too high. Lower the temperature setting of the thermostat and see if the fan is working. If it works, the problem is solved.

The thing is, it is very common for thermostats to be off by a few degrees, and in this case, the thermostat needs to be appropriately calibrated. The best solution would be to adjust the thermostat accordingly; for eg: if the attic temperature is 100 degrees F, but the fan is not working even above that temperature, then lower the thermostat setting until the fan works, and treat it as 100 degrees F. If that doesn’t work for you, the thermostat must be replaced.

Check the power supply to the fan

If lowering the temperature setting doesn’t kick start the fan, the problem could be with the motor, the thermostat, or the power socket. To check if the problem is with the outlet from the mains, connect something else, maybe a light bulb, to the mains and see if that works. If the light bulb doesn’t turn on, the fault is with the mains power. Next, check the circuit breaker to ensure it isn’t accidentally turned off. If the circuit breaker is on, but the fan is not drawing any current, you will need to rewire the connection.

Remove the thermostat

If the fault is not with the mains, then the next step is to check if the thermostat is faulty. Remove the thermostat from the wiring and connect the mains directly to the fan. If the fan still doesn’t work, the problem is with the motor, and the only solution is to replace either the motor or the entire fan.

Here is a good video about troubleshooting an attic fan;

How to troubleshoot an attic fan

2. Attic fan running non-stop (Won’t turn off)

A faulty thermostat, wrong temperature setting, or hot wiring the fan to the mains can cause an attic fan to run non-stop without ever stopping.

Most attic fans come with a thermostat controller where you can set the temperature at which the fan should turn on. A one-speed fan often comes with a single thermostat, and a two-speed one comes with two thermostats. The second thermostat in the latter case is used to set a higher temperature at which the fan should switch to the highest speed setting. In addition, some controllers come with a humidistat along with the thermostat.

An attic fan will run non-stop if the temperature you set on the thermostat is lower than the outdoor temperature. This is because the attic fan can never cool the attic to a temperature lower than the outside temperature.

The only solution to this problem is to increase the temperature setting on the thermostat. Set the thermostat temperature slightly higher than the outside temperature, maybe 10 degrees more.

Another reason why the fan is running constantly is that it is hot-wired to the mains without any controller in between. This means the fan has been running non-stop since it was installed, and in this case, the only way to shut off the fan is to turn off the breaker supplying power to it.

If you need to know more about turning off an attic fan, here is a helpful guide: how to turn off an attic fan

3. The attic fan sounds like a helicopter

That is a bit of an exaggeration, isn’t it? However, attic fans can be really noisy sometimes due to many reasons.

Noise/rattling from an attic fan is due to bent or unbalanced blades, worn-out bearings, lack of lubrication, or loose screws. These issues can cause an attic fan to vibrate violently, sounding like a helicopter.

Even though the blades are dynamically balanced and tested, they can get bent during shipping or installation.

Unfortunately, there is no way you can repair or balance a bent blade unless you are very experienced in that work. However, problems like these are usually covered under the manufacturer’s warranty, so if the blades are bent or unbalanced, the best solution is to contact the manufacturer and get a replacement. Most companies will replace the entire attic fan in these cases.

If you feel like doing a bit of experiment with fan balancing, check this video below, but beware that this may invalidate your warranty.

A video of balancing the bent blades of an attic fan

If your attic fan has a belt drive, the noise can be due to worn-out bearings. This happens if the fan has been running without any maintenance for a long time. Replacing the worn-out bearings with new ones is the only solution to this problem.

Rattling noises can also be caused if the screws of the assembly are not tightened firmly. Over time, these screws can get loose and cause vibrations and noise. If this is the case, then the solution is simple: tighten those screws!

Lack of lubrication can also cause noise. Although some attic fans come with oil ports, it is recommended to oil them yearly or bi-yearly.

To be honest, not all attic fans are quiet. If you opted for a cheaper model then the reason for the noise is not bad installation but the whole fan itself, and the only solution is to replace the whole thing. Here is a list of some good, whisper-quiet attic fans you can check.

4. Attic fan humming not working

When you turn on your attic fan, sometimes you will find that it is not working, but at the same time, you can hear a humming noise from it. And if you give the blades a slight push, the fan will keep spinning.

If your attic fan keeps humming but not working, then the problem is with the fan’s motor. To be more specific, the fan motor may have a faulty capacitor.

Here is how to test if this is the problem;

  1. Switch on the attic fan and manually push the blades a little. If the fan starts running in that direction, the problem is with the capacitor.
  2. If the fan doesn’t run even after giving it a push or two, and it keeps humming, the problem is with the motor’s winding.

If the unit is under warranty, the best solution is to get a replacement motor from them. Please check the terms of the warranty to see if they cover installation charges also.

If the fan is out of warranty and the problem is with the capacitor, then you can easily replace it yourself if you have the know-how. If the motor is gone, and your fan is a cheap one, then calling a professional for help will cost you more than the fan; the best solution would be to buy another attic fan and install it yourself.

Or, if you are confident you can get a replacement motor and install it yourself, here is a video of attic fan motor replacement;

Replacing attic fan motor

In any case, if the attic fan is humming and not running, or running slower, then immediately shut off the power to it since keeping it running will indeed cause a fire hazard.

5. Attic fan is not pulling air

If your attic exhaust fan is running fast, but it fails to pull any air, then there is definitely a problem with the intake or exhaust vents of the attic. To run a powered attic fan the attic should have at least 1 sq.ft of intake ventilation per 150 to 300 CFM rating of the fan. Even if you have enough attic vents, these may be blocked entirely or partially, making it difficult for outside air to come into the attic.

If your fan is not pulling air, then make sure that the intake and exhaust vents of the attic are properly sized and not obstructed. If the problem persists, then it is best to contact a professional.

6. Attic fan keeps turning on and off

Another problem you can face with your attic fan is it keeps turning on and off every fifteen seconds or so. This can be really annoying and reduce the longevity of your fan.

If your attic fan keeps turning on and off, it is due to the thermostat being faulty or the bad positioning of its temperature sensor. To fix this, you will have to either replace the thermostat or bypass it and connect the attic fan directly to the mains.

When the thermostat is faulty, it will fail to electrically connect the fan’s motor to the main’s power supply. This results in intermittent electrical connections turning the fan on and off. In most cases, it is not practical to repair the thermostat, so replacing it is the best option. You can also bypass the thermostat, but this will mean that the fan will run continuously unless you manually turn it off.

Here is a good guide to bypass attic fan thermostat. Also, refer how to turn off an attic fan

Another possible reason why the attic fan turns on and off is the faulty placement of the thermostat. The thermostat is designed to turn off the attic fan when the attic cools below a preset temperature. It senses temperature through a sensor which in this case is placed on the thermostat. If the thermostat is placed in such a way that the cool intake air falls on its temperature sensor, it becomes impossible to sense the correct attic temperature. Since the intake air is cool, the sensor will falsely shut off the fan assuming the cut-off attic temperature is already reached.

If this is the problem, moving the thermostat away will fix it.

7. Solar attic fan not working

If you are having a solar attic fan, you could face all the problems mentioned above. So to troubleshoot, please see if it is one of the above. If none of the above seems to be the problem, then the issue could be with the solar panels, the auxiliary power supply, or the thermostat setting.

Some solar attic fans come with an auxiliary power option to run the fan during the night. If the fan is working properly during the day and not at night, the fault is with this auxiliary power supply.

The thermostats on some solar attic fan models are preset at 80 degrees Fahrenheit (For eg: Remington products). If the attic temperature falls below this, the fans will not run. If you want the fan to run even below this temperature, then the best option is to bypass the thermostat.

The fault could be with the solar panels as well. The solar panels can become faulty due to many reasons, including cracks, debris like leaves or bird poop blocking the light from reaching the panels, bad quality material, and age. The issue also can be solar panels not getting enough sunlight, or the wires connected to them could be loose. The worst case is the solar panels become faulty, as you will need to replace them. This can be really hard if your attic fan is roof-mounted. These fans come with solar panels fixed on the domes, so it is difficult to replace them.

Also, make sure that the panels get ample sunlight. Make sure to inspect the wires going to the panels, they can get loose even if they look alright.

How do I know if my attic fan is working

I know this may sound silly, but many people owning attic fans have this problem, they don’t know whether the fan is running properly or whether it is running at all.

The only way to know whether an attic fan is running or not is by climbing into the attic and seeing it for yourself. You can also try listening to the fan noise but many fans are quiet these days so it is not very practical.

Yes, if the fan was noisy but all of a sudden the attic is quiet you can know that it stopped working. But otherwise, especially for solar attic fans, there is no way of knowing without physically being present in the attic.

Or you can put a CCTV there but you must be really crazy to do that!

I read a suggestion about tying a ribbon at the exhaust vent. While it may work for gable-mounted fans, it is not going to look very good aesthetically.

You can also install an indicator lamp at the output of the thermostat, so it will light up when the fan is running. Make sure to install it at the output otherwise the lamp will stay on even when the attic fan is not running. However, the downside of this is, that you won’t know if the fan stopped working due to any faults with its motor.

Therefore, the best way to know if your attic fan is working is by seeing it yourself.

Frequently Asked Questions

Can you repair an attic fan?

An attic fan can be repaired easily. But the real question is whether you should repair it or replace it. If the problem is as simple as a loose wire or unbalanced blades, or it is under warranty, you should repair it. However, if there is any problem with the motor, I recommend replacing the entire attic fan instead of attempting to repair it. This is because repairing the motor can cost as much as a new fan.

How much does it cost to repair an attic fan?

Repairing a typical attic fan cost between $200 to $400, including labor and parts. Considering this costs as much as a new attic fan, replacing it is the more logical choice.

How long does an attic fan last?

A typical attic fan can last anywhere from 15 to 20 years if it is properly maintained. That being said, attic fans need very little maintenance; you only need to oil it (many models don’t need this), and clean its blades once a year.

Who repairs attic fans?

Attic fans are usually repaired by an electrician or an HVAC professional.

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Charles John

Experienced HVAC technician with 8 years of experience in the industry. Capable of handling all sorts of heating and cooling equipment as well as proficient in operational management, construction-related techniques such as preventative maintenance, electrical troubleshooting and AutoCAD

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