Top 4 Causes Of Your Bath Fan Not Venting

Home » Top 4 Causes Of Your Bath Fan Not Venting

You’re looking forward to taking a long, hot shower, but you want to minimize the amount of condensation that will inevitably gather on your bathroom walls and mirror. Perhaps you’ve sprayed the tiles with a mildew and mold cleaning solution and need to vent the fumes. Or let’s say you’ve eaten something that has disagreed with you and you’re quickly heading to the bathroom to… on second thought, let’s not say not! Simply put, there are multiple reasons you want your bath fan to vent properly.

How the bath fan vents

A bath fan is not a complicated appliance. Similar to how a range vent hood will draw odors, steam, or smoke from the food you’re cooking on a stove top and force these to the outside of the home or through a charcoal filter back into the kitchen through a front vent, a bath fan uses a motor and fan blade (or blower wheel) to draw moisture or odors through its grille and exhaust it through venting positioned above the bath fan to the exterior of the home, often through a vent pipe installed on the roof. The main purpose of a bath fan is to help prevent mold growth on the walls or ceiling by removing the moisture that can cause the growth.

This is where a bath fan differs from a range vent hood. Because the moist air can be damaging, the bath fan does not have the option of channeling the air through any filters back into the bathroom. The moist air must be vented directly to the outside of the home and not into the home’s attic or crawlspace where it can warp wood or damage insulation and, yes, produce the same mold growth you wanted to avoid in the bathroom.

Why is the bath fan not venting?

Provided the bath fan has been installed properly with venting leading directly to the outside of the home without any vent termination impeding the air flow, there is some basic troubleshooting you can do to determine why your bath fan is not venting. Here are the four most common causes you should investigate:

  1. Defective fan motor – Check to see if the fan blade, or blower wheel, is spinning when the bath fan is turned on. If not, you can use a multimeter to confirm the motor is receiving power through the power supply wires connected to the terminals on the motor. If the motor is receiving power, but the fan blade, or blower wheel, is not spinning, use the multimeter to test the motor for electrical continuity – a continuous electrical path present in the component. If the motor tests “negative” for continuity, it has likely burned out and will need to be replaced to fix the problem.
  2. Defective fan switch – Depending on the bath fan model, there may be three different circuits controlling the fan, light, and heater separately. Identify the fan switch and use the multimeter to test the switch for electrical continuity. As with the motor, if the fan switch tests negative for continuity, you will need to replace the switch with a new one.
  3. Air flow problem – Over time, the bath fan’s grille will collect dust and debris, so you’ll want to make sure to clean the grille periodically, along with the fan blade or blower wheel. If the fan still isn’t venting properly after cleaning, it’s possible the vent leading to the outside of the home has become clogged, likely from leaves, seeds, or nuts from a tree with limbs overhanging the roof.
  4. Damaged fan blade or blower wheel – A damaged or obstructed fan blade or blower wheel will also interfere with venting. Remove any obstruction to free the blade or wheel, if applicable, and confirm the part is not rubbing against the fan housing. If damaged, you should replace the old fan blade or blower wheel with a new one.

Replacing the bath fan’s exhaust fan motor

So, let’s say you’ve determined the exhaust fan motor has burned out and a new motor will need to be installed. Is this something the average do-it-yourselfer can handle? With a little patience, absolutely. While the precise steps to do this will vary depending on the model, here are some general instructions that should help you get the job done…

  • Before you begin the procedure, be sure to shut off the power supply to the bath fan.
  • If your bath fan has a light built in, you will likely need to detach the light cover from the grille and unscrew the bulb before you can remove the grille.
  • Unthread the screws or nuts to release the grille.
  • Again, if the bath fan utilizes a light, the product’s reflector assembly may need to be removed at this point. Since the fan, light, and (potentially) the heater will each have separate power wires, you will probably need to disconnect the light power wires or plug from a receptacle to fully remove the reflector assembly.
  • Disconnect the fan motor wire plug from its receptacle.
  • You may need to unthread screws or nuts securing the fan housing so you can pull it down.
  • Detach the fan motor’s power cord from the housing if necessary.
  • Unthread the screws or nut securing the fan motor mounting bracket to the housing to fully remove the motor.
  • Remove the blower wheel or fan blade from the motor shaft.
  • To install the new exhaust fan motor, first align the blower wheel or fan blade on the motor shaft and press firmly to fully seat.
  • Position the new motor in the fan housing and secure the mounting bracket with the screws or nuts.
  • Secure the motor’s power cord to the housing as needed.
  • Reseat the fan housing and secure it with the screws or nuts.
  • Plug the fan motor’s power cord into its receptacle.
  • If applicable to your model, plug the light power cord into its receptacle, reseat the reflector assembly and secure it with the screws or nuts.
  • Reinstall the grille.
  • Screw in the light bulb, if required, and replace the light cover.
  • Restore power to the bath fan.

Fix your bath fan now with parts from Repair Clinic

Finding the right exhaust fan motor, or blower wheel, heater, grille, or any other component that matches your bath fan is crucial to a successful repair. This is where Repair can be a great resource. Repair Clinic stocks genuine manufacturer bath fan parts from the most prominent names in the industry, including Broan, NuTone, and Panasonic. To find the correct part for your bath fan, enter the full model number of the product in the Repair Clinic website search bar to reveal a complete list of compatible parts. From there, you can use the “Part Category” filter (Examples: “Motor”, “Switch”) along with the “Part Title” filter (Examples: “Exhaust Fan Motor”, “Fan Switch”) to identify the exact component that will work with your specific bath fan.

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