fan emitting high-pitched noise when NOT spinning!

I just bought a used Fujitsu ST5112. It works fine, but I noticed that it starts emitting an irregular, high-pitched noise about 15-20 minutes after turning it on. It's a weird sound, and it varies in pitch--almost like music but totally random. It usually lasts for 5-10 minutes, then stops. I opened the computer and used some rubber hose as a stethoscope to find the source, and I'm positive it's coming from the fan (only 1 fan in this slate computer, next to the vent). I cleaned the fan and the whole motherboard with compressed air, with no effect. The weird thing is that it's not the fan's spinning that causes the noise. It's quiet when it spins, but when it's NOT spinning it sometimes makes this noise. I read that sometimes capacitors can cause this. There aren't any visible capacitors on the fan, but there's a small chip attached to the fan's casing that might have a capacitor inside--or some other component of the chip could be making the noise.

Anyway, it looks like it would be difficult to replace the fan. The connecting wires look soldered into the motherboard, and it would be difficult to find a replacement fan for the ST5112. But I'd like to try to reduce the noise, which is very annoying. I'm wondering if I could try putting some kind of sound-damping material over the chip without causing any harm. Maybe Something like chewing gum, but a bit stickier? Any specific ideas of what might work for this use? Some kind of paste or resin that's sticky but removable, and won't interfere with the circuitry. Or any other ideas for a fix?

 

1. Clean the FAN not with air but the hard/real way. This might help. Compressed air only makes some more room, but doesn't actually clean.

2. The noise could be coming from the CPU and you just might not be hearing it while the FAN is spinning!? Try to localize the noise more accurately!

3.

I beg your pardon

It should/could stop spinning of course, what kind of a laptop do you have Oh wait - I saw your signature now - ACER - that explains a lot

Depending on whether there is a dedicated GPU or not - in the first case it should normally be on for like over 80% of the time but stop whenever idle. In the second case it could be that it just spins for 5 minutes every half an hour. This is how it was on one of my previous laptops. This is perfectly normal, as the CPU itself especially in idle does not emit that much heat.
But yes... those rules don't always apply to Acer and Fujitsu

 

yes, these kind of noise sometimes are very annoying but if it is an old machine, not much can be done about it especially you seem to suggest that it is not the spinning fan but sometime else.

some loud music is an alternative to

 

That is correct, fans do sometimes stop spinning depending on system temp, as I believe is the case with this small, low-power slate computer. And I DID localize the source of the noise, as I said in my OP. I used rubber hose with 1 end against my ear and moved the other end around the motherboard till I found the source. DEFINITELY the fan. I even unscrewed the fan, moved it outside the casing, closed the casing so that the fan was hanging out of the computer by its wires. VERY clearly coming from the fan--the system fan, which is the only fan in the computer. I think it may be a worn capacitor. In any case, the only thing that could really be causing it is a chip that sits on top of the fan, maybe to sense temp and start/stop the fan accordingly. It seems to make noise when the fan is just about to start, then gets quiet when it starts. Anyway, I think I'll just try covering that little chip with some putty to damp the sound--it's not in a place where doing that would interfere with the moving of the fan. A little chewing gum should work.

 

So why don't you just replace the FAN!? There should be a number on it - try looking for one... worst case even second-hand...

Also - send an inquiry to Fujitsu! They should be able to offer you the corresponding fan. They were able to offer me a new MB for my at that time almost 4 years old Fujitsu-Siemens (taking into account that that particular MB was only for that specific model and sub-model!). Well the price was beyond reality and close to the point I'd have thought they have made a mistake and are willing to sell me the whole laptop + upgrades, but that was a custom MB...

How expensive could a FAN be.

On the other hand Sony sells the FAN only together with the heat-sink cooling system only... if this is the case with Fujitsu as well it could by quite expensive.

But anyway worth giving it a try...

 

Good POINT, I'll look into replacing the FAN

 

You can unplug it while its running you know... nothing will explode

Its funny though, at first I was like, oh its those inductor coils again that everyone thinks is the fan... but that sounds really odd. What CPU are we dealing with here?

It sounds particularly odd because... well I still recognized the sound you're describing... my refrigerator does that

I'm curious about the possible sensor that is built on to this fan, could you take a picture?
If its a normal fan, then the noise must simply be a strange mechanical malfunction. Which is good...

Gracy, you know lots of (different) people make those fans right?
E. G. Some acers have adda AND delta fans - they look almost identical, and are used interchangeably.

Often they have a nice little model# especially forcecons BUT this is only for the motor and blades! E. G. Dell xps m1530, MSI gx620-640 and clevo m860tu ALL use the same fan BUT with different shrouds and mounts.
When you get into more popular systems, I think they often do have the same shroud. It should not be too hard to find this unless its very strange. Just don't be surprised if it was pulled from a toshiba

 

Yes, this is true My Sony for example seems to share the same FAN with a few Dells So just look into the numbers on the FAN.

And yet you removed your signature? Ok... keep it secret, still an Acer
You also use a cooler I thought external coolers' time was long over...

Joking But again - it is perfectly normal for the FAN not to spin depending on configuration and load.

 

Getting back on topic, to the OP, if you do decide to replace the fan, you might as well clean the inside of the notebook while you're at it. Compressed air works well in this regard, although be sure to not shake or hold the can upside down while cleaning the laptop out.

Also, for future reference, if you do clean the fans in your laptop, ensure that you arrest the fan blades in place before spraying air into the fan duct area as you can easily damage the fan if you allow the fan to spin around.