Asus P5P800 CPU Fan problem

By Sandaun · 16 replies
Oct 26, 2005
  1. Hi,

    I've an ASUS P5P800 MOBO. I've tried to solve a problem with CPU Fan, and now that I've solved it, I've another.
    When I put target temperature on bios MOBO, CPU Fan should increase or decrease its RPMs depending on CPU temp. Since today that was working perfect, but now it doesn't work. CPU fan keeps 2500 RPM and it doesn't increase.
    MOBO CPU sensor is working fine, so I think maybe the problem is with CPU Fan. What do you think guys??!

  2. mfquarles

    mfquarles TS Rookie


    What CPU did you use? Did you purchase the fan with the chip, bundled? Or was it purchased separately?
  3. Sandaun

    Sandaun TS Rookie Topic Starter


    It's an Intel 3,0 Ghz cpu with its original fan. Don't know what to do, I think that it is a fan problem, because mobo temp. sensors are working fine, and since today there wasn't any problem.
    The easy thing to do maybe is to try another fan, isn't it?

  4. mfquarles

    mfquarles TS Rookie

    Is your chip overheating?
    Can you be sure the fan is at 2500 rpm? I'll check your thread tomorrow to see how things go.
  5. Sandaun

    Sandaun TS Rookie Topic Starter

    Chip is overheating when I play some games like Half Life 2, or when I'm using some applications at the same time. But if I only use MSN, antivirus, etc... chip temperature is about 43 - 46 ºC.
    And yes, I'm sure that fan is at 2400 - 2500 rpm, and when processor temperature increases, cpu fan keeps on 2500 rpm...

    In 8 hours aprox. I'll try another fan, and I'll post how it's going.

  6. Tedster

    Tedster Techspot old timer..... Posts: 6,002   +15

    are you using thermal grease correctly?
  7. Sandaun

    Sandaun TS Rookie Topic Starter

    Good question...

    I'm using original fan thermal grease, but yesterday when I was trying to solve this problem, I've noticed that there was only a little bit of it.
    I don't know exactly how this grease works... I mean... could be the problem because of that??!
  8. Tedster

    Tedster Techspot old timer..... Posts: 6,002   +15

    most definately. Thermal grease works by acting as a conduit from the cpu to the heat sink.

    Use arctic silver. Spread a very thin layer with the edge of a index card or your finger in a bag over the top of the cpu. leave about 2mm from the edges. Thermal grease is conductive and you don't want it on your motherboard.
  9. Sandaun

    Sandaun TS Rookie Topic Starter

    Ok, I've another mobo Asus P5P800, and I've tried another CPU Fun, but it doesn't work. Now I don't know what to do, because I've changed everything that could be the problem. What do you think guys?

    Maybe the power supply isn't working fine? Because if I've changed mobo and CPU fun... what else can be?

  10. mfquarles

    mfquarles TS Rookie

    All I can think of are more questions, some of which may not have a direct bearing.
    For instance, how many case fans do you have in your system?
    Were the temperature readings from software, or did you use a thermometer?
    Are there other symptoms from overheating? (Does it act up when overheating?)
    Do you have the manual that came with the board. Asus manuals are tops. What does it tell you about setting the fan speed?
    Were you overclocking the chip?
    Sorry to ask so much. Just hoping you can find a solution.
  11. Tedster

    Tedster Techspot old timer..... Posts: 6,002   +15

    does your BIOS have a smart fan feature? Your fan may not come on because the CPU thermostat hasn't turned it on!
  12. Sandaun

    Sandaun TS Rookie Topic Starter

    Sure, I've QFan Asus feature. With that, I can put the temp that I want to keep. Then, when de CPU reaches this temp, CPU fan should increase its rpm to decrease temp. This doesn't work now, and I don't know why.

    About the questions: I'm using software to know cpu temp. I've only one case fan but it wasn't a problem to keep the temp fine.
    When overheating, my computer hangs up.
    And no, I'm not overclocking my processor...

    I'm repairing computers since I was 14, and this is the most rare thing I've ever seen, because I've changed everything that could be the problem (mobo and cpu fan)... Now I only think that maybe the power supply (350w) isn't working fine... Do you think that I would have to try a 400w one?

    Thanks for your answers.

    PS: I'm thinking to change this mobo for a Gigabyte one... but I'm not sure that this is going to solve the problem...
  13. Sandaun

    Sandaun TS Rookie Topic Starter

    Ok, I've noticed one thing while playing a mod of Half Life (day of defeat). While playing I was runnig Asus Probe, that shows some voltage from de Mobo. And probe has alerted me that AGP slot (3,3V) was only giving 2,8V, and then my computer hangued up. This isn't the first time that it happens, and maybe this is the reason than my computer isn't running very well (including cpu fan).

    Then, what do you think? Power supply problem or AGP card problem?
    I vote for power supply ....

    Tell me what you think...
  14. mfquarles

    mfquarles TS Rookie

    I think you may have it.
    Do, however, check the power cable to the motherboard. Look up inside the plug at all twenty of the wires to see if they are all seated properly. I know the odds are a thousand to one against that being the problem, but it would be a cheap fix if it were.
  15. Samstoned

    Samstoned TechSpot Paladin Posts: 1,018

    I think all the on board type sensers with 3rd party software speed controlled fans have problems
    I disable these in bios get a real controller with its own software.
    other wise could be bad senser.if other devices are showing drops PSU is not regulating properly
    my rule of thumb 100 watts more than It needs
    first the PSU are all inflated ratings real life electronics always works diff then whats on the board
  16. Sandaun

    Sandaun TS Rookie Topic Starter

    Solved !!

    I've bought a 500 W Power supply unit and now everything work perfect.

    Thanks !!!
  17. Tedster

    Tedster Techspot old timer..... Posts: 6,002   +15

    Not having enough power can cause overheating as well... although that is not normally the case.
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