We have had many 12v fans for when we visit hot places and they can be worse than useless, making too much noise and vibrating. Not for the first time I have just 'fixed' our little oscillating, vibrating sleep killer. As I have discovered before, they are not only cheaply made but poorly finished off. Searching all parts of the plastic fan and the moulding, I discovered little bits of the plastic that had not been trimmed off and with a Stanley knife, removed them. The fan no longer vibrates and while not silent, is now tolerable.
Alan
Alan