I have an extract fan motor in a kitchen and it is making noise when it is turned on in number 1 speed as you turn up the speed to number 5 the noise seems to fade and is barely heard when you turn it back to speed number 1 the noise is loud again. It is sealed in the ducting obviously i was thinking would it be the bearings in the motor or would it be maybe that the housing for holding the fan is loose. Would anybody have any experience with this sort of thing before if so i would be greatful for any information.
I am a refrigeration and air conditioning engineer but i have no experience with theese fans.
kindest regards bellaman