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[SOS] PC Overheating, I'm stumped

HarshLanguageHarshLanguage Registered User regular
I'm having overheating issues with my self-built PC. Here's the gist of it:

- Overheats and shut down during gaming, sometimes
- Shutdowns occur even when case is open and outside fan is blowing in
- Overheating is inconsistent, sometimes it has no problems even after many hours, sometimes its shuts down after less than 2 hours
- CPU fan showing error at boot, but is actually working most of the time.
- Case is a large tower, with 1 intake fan, 2 outflow fans, and PSU fan.
- Ambient room temp is usually around 75 degrees.

Specs: AMD 64 X2 4400+ socket 939 on an ASUS A8N32-SLI Deluxe, HSF is an Arctic Cooling Freezer 64 Pro 92mm, vid card is an nVidia 7900GS, PSU is an Antec Neo 500W.

I'm pretty familiar with PC innards but haven't dealt with overheating problems like this before. So my first step is to replace the CPU fan. I'm doing that tonight. But I'm concerned that the overheating has ocurred even when I know the CPU fan was working and the case was open with a big room fan blowing in.

So, am I looking at some other problem causing the overheating?

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Posts

  • The Rocking MThe Rocking M Brisbane, AustraliaRegistered User regular
    edited March 2008
  • ecco the dolphinecco the dolphin Registered User regular
    edited March 2008
    Maybe the thermal paste is gone? The heatsink may no longer be making sufficient physical contact with the actual CPU/GPU to actually take the heat out?

    ecco the dolphin on
    Penny Arcade Developers at PADev.net.
  • ArcticMonkeyArcticMonkey Registered User regular
    edited March 2008
    How hot is the CPU and GPU heat sinks when the PC crashes?
    If the heat sink is too hot to touch then it needs better cooling, but that is unlikely unless it's insanely overclocked or stuffed with pet hair and dust.
    If the PC crashes from overheating while heat sinks are still cool enough to touch you may have a bad fit with not enough thermal paste and/or air bubbles.

    ArcticMonkey on
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  • HarshLanguageHarshLanguage Registered User regular
    edited March 2008
    Thanks for the responses. All internal parts are totally dust-free. The CPU isn't overclocked at all.

    The heatsink, when it shuts off, is HOT. Very very hot. Burning flesh hot. I haven't seen what the temp actually is before it shuts down. But heat is definitely being transferred to the heatsink.

    I'm not very familiar with fan and speed monitoring utils, but I did install SpeedFan today. It shows the CPU fan running at 811rpm, a "Temp1" of 62 C, a "Temp2" of 40 C, and the two core temps at 63 and 45 C. That's at idle after about 4 hours of being on. I'm tempted to run a game for a while and see what happens, but I'd rather not push my luck.

    HarshLanguage on
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    > turn on light

    Good start to the day. Pity it's going to be the worst one of your life. The light is now on.
  • ArcticMonkeyArcticMonkey Registered User regular
    edited March 2008
    Thanks for the responses. All internal parts are totally dust-free. The CPU isn't overclocked at all.

    The heatsink, when it shuts off, is HOT. Very very hot. Burning flesh hot. I haven't seen what the temp actually is before it shuts down. But heat is definitely being transferred to the heatsink.

    I'm not very familiar with fan and speed monitoring utils, but I did install SpeedFan today. It shows the CPU fan running at 811rpm, a "Temp1" of 62 C, a "Temp2" of 40 C, and the two core temps at 63 and 45 C. That's at idle after about 4 hours of being on. I'm tempted to run a game for a while and see what happens, but I'd rather not push my luck.

    On SpeedFan, go to Configure and check which core is at 63c idle. A CPU fan at 811rpm seems low, especially if the CPU core is at 63c idle.

    ArcticMonkey on
    "You read it! You can't unread it!"
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  • wabbitehwabbiteh Registered User regular
    edited March 2008
    63 degrees sounds very high for idle - I'd expect closer to 40, *maybe* 50.

    Here's my guess as to what's wrong:
    PCs are supposed to automatically (well, usually) adjust the RPM of fans to keep temperatures within a certain range. Something on your CPU fan is not connected (based on the "CPU fan not connected" error you mentioned) or not connected properly (maybe the RPM sensor is connected as if it were a case fan, instead of a CPU fan or something), so the fan is not automatically ramping up - so it ends up running far too slow and not sucking enough air over the heatsink.

    I don't know much about how fan speed control is done, or connections or any of that junk. I think you can alter the speed of some fans through software, so you could try that - that's actually what speedfan is made for, so give it a shot. Or that might not work without the fan plugged in correctly... Like I said, I don't know many specifics about fan speed controls.

    Shorter version: Your PC isn't complaining that your CPU fan isn't spinning, it's complaining that the connection needed to make it go faster isn't there. Check your connections, if that doesn't work see if you can manually speed it up. If that works, figure out why it's not doing it automatically so you don't have to have a noisy fan running full blast all the time.

    wabbiteh on
  • HarshLanguageHarshLanguage Registered User regular
    edited March 2008
    I took a closer look at the CPU fan. It has a custom shroud to fit over the heatsink with plastic clips, so I can't easily replace it, even though I have other 92mm fans lying around. The 800 rpm speed number changed to 200 rpm when I restarted the machine, so there's definitely something not right. And both of those were using SpeedFan with the speed set to 100%. Tomorrow I will re-check the connection (though it is definitely plugged into the CPU fan connector on the mobo) and probably clean everything with compressed air just in case.

    HarshLanguage on
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    > turn on light

    Good start to the day. Pity it's going to be the worst one of your life. The light is now on.
  • HarshLanguageHarshLanguage Registered User regular
    edited March 2008
    OK, I've done some more checking and it does appear to be a faulty CPU fan that's causing the overheating. I did a ghetto replacement with another 92mm fan (which I can't actually connect to the heatsink, it's just sitting on top of the HS temporarily) and not only is it running at 2250rpm, the overheat warnings are (so far) gone from SpeedFan. I contacted Arctic Cooling to see how to get a replacement fan that will actually clip onto the HS like the failed fan does. (In addition to the plastic shroud with clips, the fan is attached to the shroud with rubber pieces, not screws. So replacement of the fan portion looks tough.) But they told me to contact the dealer (Newegg) about it. That's... not really helpful. I'd rather not buy a whole new HSF.

    But I still have a couple questions to pick y'alls brains about. First, the failed CPU fan had a 4-pin power connector, but my motherboard doesn't appear to have any 4-pin fan connectors on it. What does that 4th pin do? Does it carry additional speed control info to compatible mobos?

    Second, I have a question about airflow direction. I've just noticed that the CPU fan blows through the heatsink towards the front of the case, not the back. This seems odd, since if it blew towards the back, the hot air would immediately be removed from the case by the two outflow fans that are directly behind to the CPU fan. Do... do I have the heatsink installed backwards? :| I don't recall having any choice in the direction of the mounting, actually. I'm assuming this against-flow airflow pattern increases temps, but should I be concerned about it if the temps remain OK with a new CPU fan?

    HarshLanguage on
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    > turn on light

    Good start to the day. Pity it's going to be the worst one of your life. The light is now on.
  • wabbitehwabbiteh Registered User regular
    edited March 2008
    Alright, a little searching on wikipedia has learned me up about fan speed control.

    There are two kinds of fan headers: 3-pin and 4-pin. 3-pin was the original, 4-pin came later for PWM fans.

    3-pin: Ground, Voltage, RPM Sensor. The motherboard reads the RPM sensor and checks how hot the <blank> is, and varies the voltage to make the fan spin faster or slower. These usually cannot be controlled by software. Some motherboard fan controllers will switch the voltage on and off, as with 4-pin PWM fans, but they have to do it at a low frequency so fans sometimes click or get noisy.
    4-pin: Ground, +12V, RPM sensor, PWM controller. Motherboard reads the RPM sensor and checks how hot the <blank> is, then tells the fan, via the PWM controller, what percentage of its capacity it should be at. E.g., if it asked for 50%, the fan would switch between on at full blast, then off at full blast, really really quickly. If it asked for 66%, the fan would be ON ON OFF ON ON OFF, etc. These can almost always be controlled by software.

    The problem is that when you plug a 4-pin fan into a 3 pin header, the PWM wire isn't attached to anything, so there's no way to control the fan's speed and it defaults to whatever the manufacturer decided. This is *supposed* to be full speed, but often isn't. Sometimes this is full blast, sometimes this is minimum speed. In your case, it's minimum speed. Also, it seems that the way that the RPM sensor gives out its data is different between 3-pin and 4-pin fans, so the motherboard gets angry and says that no fan is connected.

    Anyway, you've got a few options.
    1. Buy a 3-pin fan - you said that your fan is attached to the heatsink strangely. Are you *sure* there's no way to use a generic fan? I've never heard of proprietary fans that *had* to be used with heatsinks, but I guess it wouldn't surprise me. Even then, if you felt like being really ghetto you could probably figure out some way to attach it.
    2. Buy a 4-pin to 3-pin adapter (I'm not really sure what these do, if anything. It seems like they just bridge the connections, in which case you're better off just doing 3., so you don't have to pay shipping.)
    3. Bridge pins 4 and 2 (yellow and blue, as seen here: http://www.frostytech.com/permalink.cfm?NewsID=54321 ) with a little piece of wire. The only worry about this is that you're supplying 12V at around 250mA to the PWM pin, when the max is supposed to be only 5V @ 5mA, so it might fry the fan. On the other hand, lots of people seem to do this, so it might be okay. There's probably something you could do with a resistor, but I forget most of my electronics classes. :( )
    4. Buy a PWM fan controller - this is silly, because they're really expensive.
    5. Use a case fan connected to your PSU's molex connectors, and just sort of jam it against your heatsink. Ghetto-tastic!
    6. I dunno. There's probably some really obvious, cheap solution that I've missed.


    More info @ http://en.wikipedia.org/wiki/Computer_fan#Connector_pin_assignment, http://www.intel.com/support/motherboards/desktop/sb/cs-012074.htm , and http://www.formfactors.org/developer/specs/4_Wire_PWM_Spec.pdf if you want to look at the specs of PWM fans for some reason.


    This was surprisingly interesting, and has gotten me to start looking at my electronics books again. Glee! :P


    EDIT: Oh, and I don't think your fan failed/broke. It probably just doesn't play nicely with 3-pin connectors.

    EDIT EDIT: Oh, and most heatsinks are set up to have the fan blowing across the heatsink (not sucking air out of, for most heatsinks at least), towards the back of the PC. If yours looks like it's one of these, then you might as well fix it if you can, if you're mucking about with your fans anyway. But if you really don't want to, and your temps are okay... then meh. It'll be a bit hotter, so the fan might spin faster and be a bit noisier, but it should be alright. Or the whole thing will explode, and your obituatry will include the phrase "heatsink shrapnel". It'd be a pretty awesome obituary. You'd probably even end up on digg or fark, so you'd be a total internet celebrity.

    wabbiteh on
  • HarshLanguageHarshLanguage Registered User regular
    edited April 2008
    Figured I should update this. Many thanks to wabbiteh for the advice. I think you're exactly right about what happened, and I'm thinking that environmental factors somehow kept the 4-pin fan in the 3-pin plug from causing shutdowns until I moved it to a new location. The replacement 3-pin fan has kept things plenty cool since I took out the 4-pin, but I still don't have a good way of attaching it. So I'm considering doing that pin-jumping trick on the 4-pin, but I admit I am a little concerned about, you know, setting things on fire or destroying either the fan or mobo. I'm going to read up about it more.

    HarshLanguage on
    QSwearing_trans_smooth_small.gif
    > turn on light

    Good start to the day. Pity it's going to be the worst one of your life. The light is now on.
  • EshEsh Tending bar. FFXIV. Motorcycles. Portland, ORRegistered User regular
    edited April 2008
    Maybe you should just spend a little money and get a whole new fan HS fan unit so your don't fry your system? Just a thought.

    Esh on
  • HarshLanguageHarshLanguage Registered User regular
    edited April 2008
    I'm not going to do anything that I think would jeopardize the system via fires/shorts/rips in the space-time-continuum. Hence the research first... didn't I say that? o_O

    The alternative is to just figure out a good way to attach the 3-pin fan to the heatsink. See above re: the custom fan shroud. This HSF is a nice unit, extremely quiet, but the downside is that it's completely nonstandard.

    HarshLanguage on
    QSwearing_trans_smooth_small.gif
    > turn on light

    Good start to the day. Pity it's going to be the worst one of your life. The light is now on.
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