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Help PC switching off but fan stays on running fast.

By scooby19730
Mar 21, 2008
  1. Can anyone help!

    I have a HP pc that has started to switch its self off but when it does this the fan will stay on but run at a really fast speed. The fan will continue to run at speed untill the plug is pulled fron the wall. This fault can happen if the PC has been on for 1 minute or 1 hour, it's totally random.
     
  2. raybay

    raybay TS Evangelist Posts: 10,716   +6

    First thing I would do is replace the fan. They are very inexpensive, and since they are built mainly by machine, they sometimes have defects. A chip defect in the fan can cause this.
    BIOS problems can conceivably do so... have you done any work, or made any changes, where a setting may have been changed, or a cable connected to the incorrect pin?
     
  3. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,911   +167

    A failing motherboard can cause this...
     
  4. Matthew

    Matthew TechSpot Staff Posts: 6,074   +84 Staff Member

    I'd put money on a defective motherboard or PSU...
     
  5. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,911   +167

    Yes Zenosincks,
    power supply could be suspected too :)
     
  6. Matthew

    Matthew TechSpot Staff Posts: 6,074   +84 Staff Member

    Err, maybe I'm taking your statement the wrong way, but I what I said wasn't a question.
     
  7. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,911   +167

    All I meant that I neglected to include a power supply in the possible causes, along with the motherboard
     
  8. scooby19730

    scooby19730 TS Rookie Topic Starter

    The strange thing is that when this happens if I hit the side of the base unit it stops and will restart ok. This has worked untill today when I used this solution to cure the problem, now it has still turned its self off I have hit the side the fan has slowed but the pc has not come on but now the base unit is beeping every few seconds.

    Does this get stranger or what?
     
  9. Matthew

    Matthew TechSpot Staff Posts: 6,074   +84 Staff Member

    Smacking your PC is not a "solution" nor a "cure". If you were smacking it hard enough, it's probably beeping because you dislodged (or damaged) a component. Open your case and reseat your components and cables. I would attempt replacing your PSU before the motherboard as it's both easier and more likely to be the cause.

    Stop beating on your machine, it's not your child and it won't solve anything.
     
  10. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,911   +167

    The motherboard or another card could be shorting to the case intermittantly. Check the motherboard mouting points for loosness
     
  11. scooby19730

    scooby19730 TS Rookie Topic Starter

    I know I shouldn't hit the thing but to someone like me who really knows nothing about computers it's the only option.

    I will open her up and make sure everything is ok (don't worry I will take care).

    I know to you guys that this will be a silly question but what is a PSU???



    I may know little about computers but I know alot about life.


    Actually no I don't.
     
     
  12. Matthew

    Matthew TechSpot Staff Posts: 6,074   +84 Staff Member

    Believe me, I understand where you're coming from with the smacking, but try to realize it's likely only going to complicate things for you.

    The PSU (Power Supply Unit) essentially converts the type of electrical power available at the wall to the type PC's can use. The PSU in a conventional desktop system is designed to convert either 120v (nominal) 60Hz AC (Alternating Current) or 240v (nominal) 50Hz AC power into +3.3V, +5V, and +12V DC (Direct Current) power.
     
  13. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,911   +167

    Yes the first thing that could be affected by banging the case would be the CPU's socket and heatsink
     
  14. scooby19730

    scooby19730 TS Rookie Topic Starter

    Thanks guys, I'm going to go and buy a PSU now and try that, i'll also check to make sure that all other bits and bobs are in place correctly. I will get back to you with an update.
     
  15. Matthew

    Matthew TechSpot Staff Posts: 6,074   +84 Staff Member

    Good luck, and hopefully you haven't caused any serious damage by teaching your PC a lesson ;).
     
  16. garreg_ddu

    garreg_ddu TS Member Posts: 29

    Nowhere can I see anything which says what make the PC/Mobo is. If it is a DELL with a system m'board made about early 2005, such as a GX280 series, then there is a known problem with the CPU heatsink temperature sensors, which may mean a new one. As Tmagic650 says above, the first thing to be affected by a bang is the CPU/Heatsink assembly, apart from the HDD which presumably is not spinning as it has powered down.
     
  17. Matthew

    Matthew TechSpot Staff Posts: 6,074   +84 Staff Member

    First post, first sentence of the second paragraph:

     
  18. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,911   +167

    HP PC? HP has a model name/number like "Pavilion 2600n"... look for it on the outside of the case front or back, or inside a CD bay or door from the front
     
  19. garreg_ddu

    garreg_ddu TS Member Posts: 29

    Oops - I missed that. Very sorry......
     
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