Bathroom Fan Takes Awhile To Start . I recently had a panasonic whisper series bath fan installed in my bathroom by a plumbing/hvac company and wired up by a separate electrician. While they require periodic cleaning, bathroom exhaust fans can keep. Bathroom Exhaust Fan Fire Hazards Countryside Fire Protection District from www.countrysidefire.com Replace the fan’s cover and enjoy the silence! The major rating starts the compressor because it uses the most energy, and the minor rating starts the fan motor. The most common cause for the bathroom fan starting slowly is the malfunctioning motor of the fan.