Replacement attic fan blades for some attic fan models can be purchased at online shops such as Sears and McCombs Supply Co. Inc. These shops carry fan blade replacements for Broan and Lomanco attic ventilators.
Malfunctioning attic fans can make a lot of noise, indicating a problem such as unbalanced fan blades, damaged ball bearings or loose screws. A fan blade can become unbalanced due to a bent blade or dents. Unbalanced fan blades tend to make loud clanging noises when the fan is in operation. It may be possible to straighten out one or more blades manually, which solves the problem. If the damage is too severe, the fan blade must be replaced.
In some instances, a noisy fan is caused by bad ball bearings, which can wear out over a period of a few years. Fixing this problem requires taking out the old ball bearings and replacing them with a new set designed for the fan's make and model. Unwanted fan noise can be the result of vibration due to loose screws. A quick way to fix a vibrating fan is to tighten up the screws so the unit no longer shakes when running. Another common problem for older attic fans is a rusted motor. Replacing a rusty fan motor is usually easier than having it repaired.