Fan noisy, grease behind fan cover - Neff Appliances Series 1 U17M42 Stainless Steel 60 cm Double Built-in Electric Fan Oven 45 l 30 l, A Energy Rating

Clean grease off the fan blades, remove the fan motor and re-secure it. Make sure there are no blades missing from the fan. Lubricate the fan shaft. Make sure any guard on the fan is not fouling and make sure the guard is properly secured. Vibration is what is likely causing the noise.

Or just replace the fan parts.

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Have you removed the cover on the rear of the refrigerator so you can test by listening there with the cover off? There also is a fan located next to the compressor and behind the rear wall of the freezer compartment.
Appliance 911 Sea Breeze

it is most likely the fan motor, you could try greasing the bearings, it is not an easy job getting to the fan motor so I would replace it .......hope this helps......cheers.

take the fan out( you have to dismantle projector) clean it out and put some grease in the bearings of the fan.
OR else just get a new fan on ebay.

Hi there,
You fan is like a vacuum that's pushing air out, rather than pulling it in. It's also a magnet for dust, so they tend to get noisy when they're clogged with dust. It's like your heart, when it's clogged with cholesterol it will pump a lot harder than a healthy heart. The best way to fix your noisy fan is to get it cleaned. You don't want to clean it with water, you want to clean it with air. If that doesn't work, then your fan is just worn and it either needs to be greased or it needs to be replaced.

Most of the problems with cooling fans in equipment is due to loss of lubrication. What anybody would do in this case is take out the cover of the receiver and replace the noisy fan, or, in case you are able to do so, repair the fan.
In fans with ball bearings, you can do nothing but disasembling the fan and replace the tiny BB, in fans with sleeves bearings, you may disassemble it, clean it well, and put some oil or light grease in it before reasembling it.

If it is the fan that is noisy, check for loose fan or the fan blades catching the cover, if all o/k, then it will probably be a worn fan bearing, only solution would be to replace the fan motor.

Is the area between your fridge and freezer smoking hot? Can you smell the rubber seals melting? Does your fridge squeak like crazy? You have an issue with your condenser fan. You can save about $50 by fixing the fan motor yourself. I'm no engineer but this was an easy fix. 1) Unplug the fridge. 2) Take off the lower back panel covering the condenser and fan. 3) Unplug the fan (on the top left from the fan. 4) Slide the fan out of the bracket 5) Take the fan blade off. (This will take the most time and TLC, it is glued on) 6) Take the two screws out of the back of the housing. **The fan motor should be free of the housing and blade** 7) Remove the two screws from the fan motor housing. 8) Pull the shaft out of the motor and clean all parts with some oil and a rag. 9) Make sure all moving parts are well oiled then put the shaft back in the motor housing. 10) Replace the motor housing screws 11) Replace the motor into the fan housing and replace the screws. 12) Slide the fan blade back onto the shaft (I used some super glue to help hold it in place) 13) Slide the fan housing back into place 14) Plug the fan into the socket 15) Plug in the fridge to make sure your fix worked (it may take a minute to kick on) 16) Replace the lower cover

A noisy fan is caused by several things. The fan can have the blade touching something behind the shroud (the back wall in front of the fan). It could be the bearings on the fan are no good - try oiling with Triflow oil. The fan blade could be out of balance. Try cleaning any dirt or grime off the blade. Fans are cheap (relatively). Tried a new one?
Some fans are just noisy. Try thin rubber between the fan and the screws that mount it (bicycle tire patches work good for this).

We have a Dell Dimension 4700C too. We had it on a 3-year warranty and the only problem with it was that from that to time it would become abnormally noisy, too noisy in fact. Dell sent a repair guy twice, and they changed the heatsink/fan assembly unit both times, and the third time we did it ourselves (it's not that hard to do), but here's the thing, we noticed how DUSTY it was when it came out, we wondered how it even worked with all that dust. So, now our warranty has expired, and guess what, the computer started making that terrible racket again, so this time, we opened it, armed with the vacuum cleaner and a can of compressed air, gave the whole inside of the computer a good once over, removed the heatsink/fan assembly and cleaned it thorougly (you can't do this unless it is out), and it worked like a charm, can't even tell the computer is running. Hope this helps.