PC front fan revving noisily up and down - no correlation to PC activity

[Radioactive]

Hi all, I hope you can help me, I have recently been having a very bizarre issue with the front fan on my PC. I have had this PC for over 2 years, with no significant problems. I recently went on holiday for two weeks and so my computer was unused for that time. When I return, I have found that the front fan is revving up and down and making a considerable noise. It doesn't do it all the time, but maybe 70%. What is odd is that there is no correlation with what I am doing at the time, the PC can be idle, I can be playing a game, it can be newly restarted - nothing I do seems to effect whether the fan is revving or not. I have opened up the BIOS and determined that it is not a fan that I can control (I.E. not the CPU fan). I can see which fan it is, it is mounted at the front of the PC (right next to the HDD). My PCs performance has not been effected in any way, Speccy does not indicate that any of the components are overheating, all the other fans are working as they should.

Does anyone have any suggestions as to what could be causing this issue? I'd happily provide my PC specs but I'm not sure which ones are relevant!

 

[Kshipper]

When you went into BIOS you should have observed the RPM. Watch to see if that is really changing speed as you say it is. I suspect that you have a bad fan bearing and that is causing partial resistance ..hence the speed changes. Just take the fan out---measure and replace it. I bet that solves everything for you! =)

 

[Radioactive]

Hi Kshipper, thanks for your advice. I can see the fan changing speed - it spins up and then drops down again. I don't think this fan is controlled in the BIOS - I could see two fans that I could control, manually turned them both up to maximum, and I could hear them change speed but the revving fan continued as normal.

Saying that I will change out the fan - its not an expensive part and if it stops this weird noise then definitely worth it. Its just odd that it has randomly started happening. Thanks very much for your help!

 

[Kshipper]

Happy to help! I was thinking that if the bearing has partially seized that would explain the sudden noise as the fan struggles to overcome the resistance of the worn fan bearing. I sure hope replacing it fixes it for you. =)