How to Repair a Bathroom Exhaust Fan
Bathroom exhaust fans are installed to remove moist air from the room to improve indoor air quality (IAQ). You can repair a defective exhaust fan without replacing the entire unit and you can clean the motor and blower fan to improve airflow and extend the life of the motor.
Dirty Exhaust Fan
Before you replace the Fan
You should check to see where the exhaust fan is terminated. Most exhaust fans are ducted to the outside of the home, but at times the exhaust fan outlet is left open and exhausts into an attic or near an attic vent.
While many local codes allow for bathroom exhaust fans to discharge into the attic or at a soffit, roof or other vent, this practice is no longer considered acceptable. Both the EPA and the American Society of Home Inspectors (ASHI) now consider this a defect. In addition, the manufacturers of bath exhaust fans provide specific installation guidelines which recommend that they be vented directly to the exterior through a dedicated vent.
A dedicated vent is one that is specifically designed for and only used for one purpose. Most exhaust fan vents have a built in flap that allows airflow out but not back in, such as a dryer vent. An existing roof, gable or soffit vent is not designed or specifically intended for this application. These vents are meant to provide proper airflow throughout the attic. Blocking any of these vents with bathroom vent pipes restricts the intended airflow. This can lead to back drafting or premature deterioration of the roofing surface due to interior temperatures and humidity. In addition, the warm moist air that is discharged through the pipe can cause wood rot and fungal growth. This can result in structural integrity issues and potential health risks.
Exhaust Fan with Dedicated Roof Vent
Tools and Materials
Replacement Motor – Locate the model number of the exhaust fan to order a replacement online or from a local hardware store or electric supply house.
Replacement Blower - optional
Replacing an Exhaust Fan Motor
Replacing an exhaust fan motor is relatively easy as most manufacturers make the unit with a removable mounting plate for the motor and a standard 2-prong plug for the electrical connection. In some instances the motor may have a smart plug or Sta-Kon connectors.
1. Pull the grille down and pinch the springs to release them from the housing. Then vacuum out the dust so you can find the model number. Old exhaust fans may have surface-mounted screws to secure the cover.
2. Remove the motor plate to access the fan motor and blower wheel. There is usually one screw that holds the motor plate in place. One side of the plate can be lowered and the other side of the plate has tabs that can slide out to remove the motor and blower assembly.
3. Unplug the motor from the internal power supply. Remove the blower wheel from the motor shaft. The plastic blower wheel typically slides only the shaft and is held in place by friction. Some older models may have a metal blower wheel that is secured to the shaft by a set screw which can be removed with an Allen wrench. Once the blower wheel is removed, remove the motor from the motor plate by removing a pair of screws or nuts from the base of the motor.
Replacement Motor with Blower Wheel attached
4. Clean the old blower wheel and motor plate with a rag. Vacuum the inside of the exhaust fan housing that is in the ceiling. This will not only improve air flow, it may cut down on noise.
5. Install the new motor and reattach the blower wheel.
6. Plug the motor back into the power supply in fan housing and secure the motor plate with the retaining screw.
Replacing an exhaust fan motor will remove moisture from your bathroom and reduce the chance of mold and mildew growth.