Heater fan noise

Hey all,

This is a rather minor thing, and being an Elise owner, rattles and minor noises are something you don't even notice after a while.

With that being said, I have noticed a recent noise coming from the heater/ac fan when switched on - sort of like a rattle as if it were off balance or something. Of course you dont hear it too easily once you get going (especially over the Stage II exhause) but I am wondering if anyone has encountered this and knows how to fix it? I am concerned mostly about a bearing being gone or some premature wear occurring that I should put a stop to.
Might be of note that it is cold here in MD and that may be affecting/ contributing to causing the noise. The car came from near LA so it has not been exposed to this kind of cold before.

Thanks in advance!

-Will