Why is my PC overheating?

December 29, 2005 1:36 PM

My computer is making a funny noise and overheating. Can you help me fix it?

My PC is occasionally making a buzzing noise. After being on for a few hours, it overheats. I hear a tone that the BIOS identifies as "CPU overheating/unseated" (or similar).

It is an older PC, about 6-7 years old, made by a company called Quantex. I've added some memory, a CD burner, a SCSI card, and a firewire card, so I've poked around inside several times. This time, I've opened it up, and the front fan and the fan mounted on the CPU heatsink both appear to be working fine. However, the power supply was pretty warm when I just opened it up, and its fan was kicking out warm air. Everything is quite dusty inside, including the fans and the power supply.

At first, I thought it was the CPU fan, but that thing looks OK. Now, I'm thinking the power supply is overheating and heating up the CPU.

Soooooo, what now? Should I blow out all the dust with compressed air? Should I replace the power supply? I'd prefer to not go to a repair service, I'm a broke student and I'm planning on replacing this PC in about a year. I'd also rather spend my Christmas money on an external hard drive. I am, however, willing to pay for a decent power supply if that's what it needs.

posted by MrZero to computers & internet (17 comments total)

you could wait til it makes the funny noise and try to see which fan it is. if i were you i'd replace teh fan on the cpu cooler just to be safe - mine died two weeks ago and it managed to cause quite a lot of trouble.
posted by andrew cooke at 1:45 PM on December 29, 2005

Clean the dust out first, then look into replacing the CPU fan like andrew said. If it's overheating, these are the two likely culprits. I'd also make sure there's a clear air path inside the case and that cables aren't hanging in the way from some past change to the guts of the system.
posted by mikeh at 1:50 PM on December 29, 2005

this happens to me after i move and fans fall off from where they're supposed to be and onto power cables. but since you've looked inside, all i can offer is a cable somewhere is probably pushing up against a fan and slowing it down (hence buzzing!). turn it on with the case off and check it out when the buzzing happens.
posted by soma lkzx at 1:59 PM on December 29, 2005

The buzzing could also be a fan that's misaligned or with dust that has gotten into the motor - both of which will slow the fan down.

After identifying which fan is buzzing, replacing it would be the best option. Putting a drop of very very light oil into the motor may provide an interim solution.

If its your PSU that's making the noise, it's possible that the fan isn't spinning as fast as it should. Replacement would be the most prudent thing to do (there are potentially some nasty capacitors in the thing - you wouldn't want to give yourself a shock poking around inside it).
posted by PurplePorpoise at 3:14 PM on December 29, 2005

Most BIOSes have fan speed monitors. watch those for a bit and compare them to what the mobo (or PSU) says is a reasonable speed.
posted by devilsbrigade at 4:10 PM on December 29, 2005

If the MB thinks the CPU is overheating, it probably is, and it probably has nothing to do with the power supply. Clean out all the dust and then run some burn-in programs, and/or run memtest.

I don't think the power supply can heat up the CPU in any sense, but certainly not in the direct way that you seem to be thinking about - the power supply takes case air in, heats it up, and blows it outside where it can't effect the CPU. Almost all power supplies blow hot air, in part because the air is already heated by the CPU and other parts before it ever gets to the supply - it shouldn't be a concern.

Keep in mind, you can get a whole PC (with windows license, if that matters to you) that is significantly faster for around $100. Swap in the improved parts that you have in the existing system, and you have a huge upgrade for not much money.
posted by Chuckles at 4:41 PM on December 29, 2005

On this most recent reboot, I have discovered that the buzzing noise is being caused by the power supply fan. I will be blowing out the dust now, and giving it a reboot to see if the dust is the only problem.

Thanks for the help so far. I hope I don't have to replace the power supply...that's a whole other AskMe thread!
posted by MrZero at 5:24 PM on December 29, 2005

OK, I blew out a ton of dust, and the power supply fan is still buzzing, and struggling to spin at all. The CPU and case fans are spinning fine. This suggests to me that I should replace the power supply. Where should I get one? I know that I can order online for cheap, but I'd prefer to purchase one and have it in now. Any decent brick-and-mortars?

(My PSU and CPU are side-by-side, which is why I think that the power supply is causing the CPU overheating alarm.)
posted by MrZero at 6:04 PM on December 29, 2005

This is a common problem. Power supplies are cheap -- just get a new one. Pay a little extra for a good one (not so much more power, more like better quality). Don't scrimp. I'm on my 3rd or 4th PS on my 1998-vintage 350 MHz screamer.

Personally I like to pay extra for quiet power supplies. Silence is golden.
posted by intermod at 7:52 PM on December 29, 2005

Never skimp on the power supply. It's the easiest thing to bump up to a slightly more expensive and vastly VASTLY superior product compared to the bottom of the line. A bad power supply will ruin your month.
posted by cellphone at 10:07 PM on December 29, 2005 [1 favorite has favorites]

Well, I went and bought an Antec SP-500 power supply. When I attempted to install it, two of the leads on the connection to the motherboard came loose and refused to connect - but I did not notice. I then repeatedly attempted to power it up, which may have burned up the motherboard, because it won't boot up at all.

Definitely ruined my month.
posted by MrZero at 8:51 AM on January 3, 2006

is your computer a dell?

what do you mean by "leads on the connection to the motherboard"? on my motherboard the power supply plugs into a socket mounted directly on the board. so are you talking about a wire between the power supply and the plug that connects to the mobo? or have you damaged the circuit board tracks on the board?

what does "it won't boot up at all" mean? do you hear any beeps? do any fans start? can you see any change at all between having the socket at the wall plugged in or not?

i'd be surprised if you've damaged your mobo by not plugging something in. it can be very frustrating when this doesn't work, but i wouldn't give up hope yet.
posted by andrew cooke at 9:09 AM on January 3, 2006

My computer was made by a company called Quantex back in 1999 or 2000. It has Award BIOS.

The problem with the Antec power supply was that two of the wires from the PSU popped out of their plug when I attempted to insert the male end from the PSU into the female end on the mobo. Although the male and female plugs fit together, two of the wires were pushed out of the male plug and did not connect with the mobo. (Diagrams or photos would help here, sorry). The motherboard itself appears fine, nothing is cracked that I can see. However, I probably powered it up about 20 times over two or three days before I noticed that these wires were not connected.

When I power it up with the old PSU, it gives me a single, repeating beep that my BIOS translates as "memory error." All the fans run and the hard drives spin. I reseated/rearranged my two sticks of memory, but continued getting the error tone, so I wonder if the memory got zapped.

I plan on taking the whole tower to a friend who is an IT pro this weekend, for more analysis. I returned the Antec PSU as defective because of the loose wires. I reinstalled the old PSU, which has a bad fan but still provides power, for experimentation purposes this weekend.
posted by MrZero at 1:01 PM on January 3, 2006

ah. ouch. a lot depends on which wires, i guess, and what else they might have touched by accident. good move taking it to a friend. this kind of thing is a lot easier to fix when you have spare computers you can swap parts with. motherboards themselves aren't expensive to replace, but it's best to be sure what's wrong first and you may just want to cut your losses and get a new one if it was old (sometimes you can't update to the latest high-ish performance parts and still remain compatible with whatever other components you have, so you end up fixing things but not getting much better performance).
posted by andrew cooke at 1:11 PM on January 3, 2006

Yes, I am willing to replace the system if necessary. I've gotten my money's worth out of it, so I'll probably put the remnants for sale on Craigslist and buy a laptop.

By the way, andrew, thanks for actually keeping tabs on the thread after it dropped off the radar. It took me a few days to get my spare laptop (equally old) up and running with a network card, so I didn't expect anyone to be hanging around anymore. I appreciate it!
posted by MrZero at 1:39 PM on January 4, 2006

no probs (credit goes to matt for the "my comments" feature!)
posted by andrew cooke at 7:05 AM on January 5, 2006

Finally, this is resolved. My friend put in new RAM and a new power supply. Apparently, the missed connection somehow ruined my RAM when I powered it up. He also had much difficulty seating the power supply to the motherboard.

Motherboard, BIOS, CPU, and everything else was fine. I am up and running now.

PS Rule of thumb: back up data first, attempt repairs second!
posted by MrZero at 3:32 PM on January 8, 2006