The motor is likely shot.. Now I could give you my opinion of those vent fans but.. Alas.. I don't really like using that kind of language (Sad grin). so I will tell you what I did.
I got 4 4" "Computer" fans (Actually I got either 10 or 12 for 10 bucks when last in Quartsite) and wired them in aparallel. I set 'em on wood spacewr (A couple of craft sticks thick works nicely) so they don't rub the screen.. Far more air flow, Much less noise, and they work. Also less electronic noise since the computer fans are "Brushless".
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times