FAN ON OVEN HAS STARTED TO MAKE VERY LOUD RATTLE

by loud noise do you mean squeeling squaking .
then its the fan bearing just order another fan motor.

It sounds like the fan itself is bad. they can get loose and start to rattle or rub against the frame.

I would suspect that the problem is caused by the external cooling fan located under the outside cooker cabinet housing, which continues to operate as the oven is cooling down if it is built in, you will have to remove it from the oven housing to access the fan

It should fit without any problem most oven housings will accomadate most ovens, those in production now, and those made 10 or more years ago.

There may be a problem with the cooling or extraction fan on the oven. All Neff appliances come with a two year manufacturers warranty, so I would advise you call them out on 0844 892 8999. If you attempt a repair yourself, you could invalidate the warranty.
All the best.

the humming sound is coming from the "squirrel cage" fan in the back of the unit, there may be some resonance vibration from the fan this issue should be addressed by a qualified service tech, the whole wall oven needs to be pulled out, i would have him check the fan.

either will work, fan bake will give you a more even cooking though

Yes, it can be fixed quite simply.
First check that the fan is not catching the cover or grill, if it is not remove panel covering fan and see if the fan blade is loose,on the shaft, they are usually held on by a left handed nut., so to tighten go the oppisite way to what you normally do, if that does not cure it, then your only solution is to replace the fan motor complete.
Plz rate my solution.
Thanks, and a merry xmas.

The exhaust fan on my oven (Aosc3040) is loud also and has always been. Just hope nothing significant brakes because this model has been discontinued and it is difficult to get parts for it. I have been told by Amana that the life expentency of this oven is 10-13 years, so don't invest in anything that is not necessary. The glass door broke on mine and I cannot get a replacement piece. My kitchen looks terrible. It is a shame because the oven works great. Linda

probable fault to earth of circular element - gets worse when element hot. you will need a megga to confirm this.