I hope you got a b-i-g discount on it, 'cause that is
not normal, and no manufacturer's warranty to help since you bought it used. But if you can turn it off, or it doesn't bother you, then "do your thing"!
@Basslie, you are now member #1776 in the Fender Rumble Club. Congratulations and welcome. Put that number in your TalkBass Signature for safe keeping. Then make yourself at home here and on
your Rumble Club Wiki page, the repository of all Rumbling wisdom and knowledge.
Many Rumblers turn the tweeter off for playing bass and only use it when playing music thru the Aux In. My own 10-year-old Rumble 500 combo makes no such extraneous noise! I can never tell if the tweeter is on or off, and I've never heard the fan. I was a 15" snob until getting this Rumble, which sounds just as good as any of my 15s, but about half, or less, of the weight!
So, Basslie, how about telling us a bit about yourself, such as your bass experience in general and your Rumble journey in particular? You'll fit right in here since we have all kinds. But we all love to ... ... ...
Rumble On!
.