Attic fan not working? Here are the common problems and their solutions

Attic fans require the least maintenance of all home equipment. But there are some occasions when they fail to work. In most cases, the reason for this is associated with a faulty motor or a faulty thermostat. Troubleshooting the attic fan will help you identify the problem and rectify it.

I have to warn you first that in most cases there is no way to repair a damaged attic fan, you will have to either replace 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. If the fan is covered under warranty the manufacturer will replace the fan for you at no cost.

Attic fan not working? common problems and their solutions

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

Attic fan problems and their solutions

1. Attic fan running non stop

An attic fan that runs non-stop is a common problem associated with the fan’s thermostat. As you know 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 2 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. Some controllers come with a humidistat and a thermostat combines.

If the temperature you set on the thermostat is lower than the outdoor temperature then the attic fan will run constantly. This is because an attic fan can never cool the attic to a temperature lower than the outside temperature value.

The only solution to this problem is to increase the temperature setting on the thermostat. Set the temperature to a value that is 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 was running constantly 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.

2. 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 a fan is often caused by loose parts or unbalanced blades. The blades of attic fans are dynamically balanced and tested but they can get bent during the shipping or installation. Unfortunately, there is no way you can repair or balance a bent blade unless you are very experienced in that work. Problems like these are usually covered under the manufacture warranty, so if the blades are bent or unbalanced the best solution is to contact the manufacture 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 then the noise can be due to worn-out bearings. This happens if the fan was running without any maintenance for a long time. Replacing the worn out bearings with new ones is the only solution for this problem.

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

Lack of lubrication can also cause noise. 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.

3. Attic fan humming not working

If your attic fan keeps humming but not working then the problem is with the motor. To be more specific, your motor may have a faulty capacitor. Here s how to make sure it is the problem;

  1. Switch on the 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 period the best solution here 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 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 surely cause a fire hazard.

4. Attic fan 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 completely 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 are not obstructed. If the problem still persists then it is best to contact a professional.

5. Attc fan not working

This is the case where the attic fan is not turning on or humming. 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.

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, problem 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 calibrated properly. 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 then the thermostat needs to be replaced.

If lowering the temperature setting doesn’t kick start the fan then 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, may be 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. Check the circuit breaker to make sure it isn’t accidentally turned off. If the circuit breaker is on but the fan is not drawing any current then you will need to rewire the connection.

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 it.

Here is a good video about troubleshooting an attic fan;

How to troubleshoot an attic fan

Charles John

A novice DIYer who learns about home ventilation. I am a mechanical engineer and have a basic knowledge of HVAC systems but I learn continuously to make myself the best blogger in that space.

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