i also had this problem. turned out it was loose screws. try that. though the noise is still there, but only at a minimum. and im gonna try spraying some lubricant on it pretty soon, see if that helps.
I've started to have this problem too. It is the A/C fan and only screeches sometimes. It seems like it happens more often when it is hotter out (85+ degrees). What do I need to lubricate, and which screws do you think could be loose? Thanks in advance!