Welcome to the Wikipedia Computing Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.
Hello! So I have 2 questions that are kinda related to each other. First, on my PC, I noticed that dust likes to build up on the "Vent" on the right side of case which, when I take that side of the case off, leads to the CPU fan. Is the CPU fan supposed to be sucking air in or blowing air out, and would dust build up on the vent be a sign that's it's blowing the wrong direction? My second question is, is the CPU fan supposed to be crooked and if so, why? ― Blaze The WolfTalkBlaze Wolf#6545 15:54, 9 November 2021 (UTC)[reply]
Every few months (or weeks, if it's bad) you should clear out the dust. Turn off and disconnect the PC (so that you can turn it around and upside down), use a vacuum cleaner hose over all vent grilles and other openings, including those underneath. Never point a vacuum cleaner hose at a fan that is rotating under power - you could cause it to rotate the wrong way and burn out its motor. Then open the case and use the vacuum cleaner hose on all fans and internal grilles (such as the side of the PSU) and any areas where you see dust buildup. If there's a thick buildup, try dislodging it beforehand with a gas duster - also use this to blow between the fins of heatsinks. Take care not to suck up any cables, particularly not the flat semi-transparent ribbon cables often used for CD-ROM drives and similar - get one of those up the hose and it will crease, possibly fracture. Don't use fluffy pipe cleaners, the wire core can cause damage.
CPU fans should sit close to the associated heatsink (many are fixed together with four screws), and the heatsink must be flat against the CPU, the heatsink is usually clipped or bolted to either the CPU or its mounting socket - check that the clips are not dislodged. One of my two Dells has a fan that looks wonky, because it's a Sunon centrifugal fan like this but larger, it's bolted to a heatsink assembly that is itself bolted through the motherboard to the chassis. The combined fan/heatsink together are massive, bigger than the Seagate Barracuda 3.5" HDD next to it.
Whatever the form, it deserves a good dusting every so often, to avoid this. --Redrose64 🌹 (talk) 17:06, 9 November 2021 (UTC)[reply]
@Redrose64: Wait what? I've always heard that you should NOT use a vacuum cleaner on a PC because there's the possibility of it shorting out the internals because of static electricity. I'm not able to provide an image of what the inside of my PC looked like before I cleaned it out at the moment, but the internals have remained in the same place, just less dusty. ― Blaze The WolfTalkBlaze Wolf#6545 18:57, 9 November 2021 (UTC)[reply]
@Blaze The Wolf: Any references for that? I've used vacuums for years to clean out computers both at home and at work. What is essential though is to never let the nozzle of the vacuum touch any part of the machine, and to never use a brush attachment. Keep the nozzle about ½" at least away from all boards, cables, fans and connectors. Martin of Sheffield (talk) 09:19, 10 November 2021 (UTC)[reply]
@Martin of Sheffield: Interesting. Well, that's better to use than just using a toothpick to clean out the dust. Thanks for telling me a vacuum won't break my computer. ― Blaze The WolfTalkBlaze Wolf#6545 14:30, 10 November 2021 (UTC)[reply]
I'm not offering any guarantees, just experience! I've used domestic vacuums on my current mini-tower at home, and that has a BIOS date of 01/06/2014 so is probably not far off 7 years old. I've used a professional vacuum (ie not one of these EU-castrated ones we get now) on IBM kit (systems, disk shelves and tape systems), Silicon Graphics (Altix and Origins) and Crays in the past with no ill effects. I've also seen them used on Alphas and VAXen, but they didn't accumulate dust as much as modern machines. Martin of Sheffield (talk) 14:45, 10 November 2021 (UTC)[reply]
@Martin of Sheffield: Alright! And then for my other question, why is the CPU fan tilted? I don't have the ability to upload a pic of the inside of my PC to show you what I mean at the moment, but it doesn't seem to be alligned with how the CPU would be (the corner isn't lined up with the corner of the CPU relatively). ― Blaze The WolfTalkBlaze Wolf#6545 15:15, 10 November 2021 (UTC)[reply]
Sorry, can't help with that one, I'd need to see a pic. See Redrose64's comments above. Martin of Sheffield (talk) 15:34, 10 November 2021 (UTC)[reply]
I'll see if I can provide a pic when I can. ― Blaze The WolfTalkBlaze Wolf#6545 15:39, 10 November 2021 (UTC)[reply]
@Martin of Sheffield: Also, should the CPU fan be blowing air out and away from the CPU or be sucking air in, towards the CPU? ― Blaze The WolfTalkBlaze Wolf#6545 15:39, 10 November 2021 (UTC)[reply]
That's a very good question! I opened up the case (not normally advisable on a running system) but am still not certain. You may be able to find an arrow on the side of the fan, that's the direction of air flow. Martin of Sheffield (talk) 16:02, 10 November 2021 (UTC)[reply]
@Martin of Sheffield: This image is what the inside of my PC looked like and shows what I mean by a crooked CPU fan. ― Blaze The WolfTalkBlaze Wolf#6545 17:02, 10 November 2021 (UTC)[reply]
It certainly looks wrong to me. Judging just from the photo, there appear to be three standoff to mount the fan to, I also think that having the fan touching the memory cards(?) is wrong. Looking at the link Redrose64 supplied confirms that the fan should be sucking the air over the heatsink and blowing it out into the case. Martin of Sheffield (talk) 18:11, 10 November 2021 (UTC)[reply]
@Martin of Sheffield: Don't know if it is touching the RAM or not (didn't actually look when I was taking the picture), and how would I remount it to correctly be on the standoffs? ― Blaze The WolfTalkBlaze Wolf#6545 18:15, 10 November 2021 (UTC)[reply]
Sorry, but that's something that could only be decided by the person on the spot. If you are touching the board, remember to ensure you are equipotential bonded with the case. Systems are a lot more robust than they used to be, but walking across a carpet can generate kV potentials. Martin of Sheffield (talk) 19:20, 10 November 2021 (UTC)[reply]
@Martin of Sheffield: Equipotential? What's that mean? Also I'm talking about how I would attach it to the standoffs. Do I need some sort of tool or can I just pick up the CPU fan and place it on the standoffs? ― Blaze The WolfTalkBlaze Wolf#6545 19:22, 10 November 2021 (UTC)[reply]
Equipotential = at the same (electrical) potential. Commonly done by professionals with a wrist strap, but can be done by amateurs by keeping one hand holding onto bare metal in the case. As regards the standoffs, no I can't help further here, you need to examine them and probably use a screwdriver.
Alright thanks! I'll look it up and see what I'm told by the internet (who has lied to me before by saying that the CPU fan being crooked like that is normal) ― Blaze The WolfTalkBlaze Wolf#6545 19:32, 10 November 2021 (UTC)[reply]
In your photo, the fan is square with a mounting hole at each corner, I would expect to see a bolt through each one. There are three standoffs visible, I would expect four - one at each corner of a square; perhaps the one at bottom right is hidden by a cable. It looks as if somebody has removed the bolts from all four corners, rotated the fan body by a small amount, then refitted the bolts. What you're aiming for is the fan to be firmly fixed to the standoffs using all four mounting holes. Standoffs are made in various styles, it is not easy to describe their assembly in a manner that covers all cases. There may be washers or other small parts that are easy to drop into an inaccessible place. Don't unscrew anything all the way unless you can be sure that any parts that are released can easily be collected. Note carefully which order they come in, particularly if there are both metal and plastic parts - plastic parts are often used to prevent metal-to-metal contact.
I don't think it matters much which way a CPU fan blows, unless it is in proximity to another fan - you don't want them to be pulling (or pushing) against one another. The main thing is to ensure a good airflow over the heatsink. --Redrose64 🌹 (talk) 20:49, 10 November 2021 (UTC)[reply]
@Redrose64: THanks for the clarification! I'll see how the standoffs attach to the CPU fan and fix it. ― Blaze The WolfTalkBlaze Wolf#6545 21:40, 10 November 2021 (UTC)[reply]
Maybe everyone is being polite, but I'm surprised that fan is turning at all, given the amount of cigarette smoke-encrusted dust and crap stuck to it. I would suggest some sort of bodge has happened. The fan appears to be too big and the wrong design, I can't even imagine how it's actually held in place. It should look a bit like this:[1] although there are many different designs. I don't think that the fan should be attached by the four large screws, which normally hold the heat sink firmly onto the CPU itself. One screw may even be missing. The correct type of fan may use small screws which screw directly between the radial fins of the heat sink as in the link. Your motherboard manual may show what a proper one looks like and how to replace it. You may be able to locate just a replacement fan, rather than a complete heat sink and fan assembly: this could be a bit tricky to install and you would need some thermal paste as well. MinorProphet (talk) 02:39, 13 November 2021 (UTC)[reply]
