What do you do when a fan on your computer is loud enough to be disruptive to your work-flow, or is ruining the fun when doing other things? Today's SuperUser Q&A post looks at the best way to catch the 'guilty culprit'.

Today's Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

Photo courtesy of el_finco (Flickr).

The Question

SuperUser reader 'Annonomus Person' wants to know how to find out which computer fan is being so loud:

On my new computer, the fan(s) is/are plain LOUD! Using SpeedFan, I find that my temps are all under 32 degrees C with normal usage (IDK how accurate that is, but the CPU itself says 27 degrees C).

The fan doesn't sound unbalanced, and it isn't making sounds in a rhythm (not the usual rrrrrrrRRRRRR… rrrrrrrRRRRRR… rrrrrrrRRRRRR… rrrrrrrRRRRRR), it just runs constantly. I am thinking about oiling the fans, but I can't decide if it is the PSU fan, a case fan, or the CPU fan. If it's the CPU fan, I will most likely just replace it with a quiet fan. How can I tell which fan is making the noise (if not multiple ones)?

One thing that I think may be the problem is my CPU fan isn't PWM, so would swapping that out help? There is no "linear voltage" or etc. thing in BIOS, so I think it may be running at full speed. Also, there could be too much airflow because it is also making a whistling noise that you can hear when close to it, and sounds like when I accidentally put part of the side cover over my floor vent to get it out of the way.

What is the best method for finding out which fan is being loud?

The Answer

SuperUser contributors Hefewe1zen, Darrel Hoffman, and Ross Aiken have the answer for us. First up, Hefewe1zen:

Use a small piece of plastic (like a pen cap) to stop the fan from spinning. That is the easiest way to isolate the cause. It's okay to stop it for a few seconds while on. Most fan noise is due to failure of the bearings. Sometimes, lifting the sticker on the hub and oiling it with 3 in 1 lube will help with the noise.

Followed by the answer from Darrel Hoffman:

We used to do this on one of our older computers and it worked fine, but a word of warning – while a plastic pen cap is probably okay, DO NOT use anything conductive like a paper clip, especially on the power supply fan. A colleague of mine knows this from experience after getting a very nasty shock and tripping all the circuit breakers. He's lucky he wasn't killed – there's supposedly enough charge in a computer power supply to be lethal.

And finally, the answer from Ross Aiken:

I'll just put this here as an alternative solution:

Unplug each fan, one-by-one from the motherboard (or from the PSU, depending on the fan), and when you stop hearing the noise, plug them back in one-by-one until you hear it again (to verify that the one you thought was making the noise actually was). I'd do the CPU fan last; everything else will be fine with ambient cooling for an extended period of time. The CPU fan is the one most likely to have issues.

Granted, if you have a GPU with fans on it, you'll probably need to use @Hefewe1zen's method for those.

I just don't like telling people to put hard objects and/or fingers near fast-moving objects. Too high of a chance of someone hurting themselves (especially if they're un-coordinated).

A fan-by-fan approach, with a good measure of caution to avoid a nasty shock or injury, is definitely a good way to learn which fan is being loud.

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

The above article may contain affiliate links, which help support How-To Geek.