PC won't start, help needed to identify problem

I was working on my homebuilt desktop system when it just cut out with no prior warning.

The motherboard is receiving power indicated by two leds.

Trying to re-start, I noticed that the fan for the CPU didn't start. This is a Crossair liquid CPU cooler - nothing complicated, straight out of the box. It has its own back fan, and an additional fan that is powered from the motherboard. Neither starts.

There is also a fan to cool the hard drives. This doesn't start either.

Nothing appears on the monitor when trying to boot, the machine will start up but not get as far as displaying anything on the monitor. No beep sequence, this mobo doesn't have a speaker.

I am unsure what exactly to make of this - what could have happened?

Did the CPU pop? (it's 3 years old but was only used for under two years)
Or is it more likely to be the motherboard after all?
Could all the fans have suddenly malfunctioned?
Does the CPU fan start if the CPU is dead? Or is the fact that the fan doesn't start, a sign that the CPU is dead?

How should I go about troubleshooting this?
Is it worth taking out the cooler to physically inspect the CPU - would I be able to smell it if the CPU died?

Very grateful for any tips!
8 answers Last reply Best Answer
More about start needed identify problem
  1. Power supply and motherboard are suspects #1 and #2. Sometimes a power supply will partially fail, producing results similar to yours. If you have another PSU to try then do so. If you would need to go out and buy a new one then we should try some other tests first. Try looking over this

    Try re-setting CMOS and re-seating both the RAM and video card, and post your full system specs. Handle parts with care and touch the case to avoid static discharge.

    CPUs almost never die, so leave off worrying over that.
  2. Notherdude, thanks for the response!

    I will follow your instructions.

    However, I would think it's not the PSU--- it's only a couple of months old - a Corsair 700W PSU. What do you make of that?

    The fan for the CPU is also only a few months old - replaced it back in Jan. Corsair liquid cooled, fairly basic model.

    I thought CPUs could easily die if they got overheated?

    So my worst case scenario was that the heating stopped working, the PC failed to shut off and it was fried.

    System spec coming up, bear with me.
  3. Motherboard: Asus P8P67
    CPU: Intel i5 2500k, overclocked at 40% but temp always showed 40C or less.
    PSU: Corsair CX750M
    Hard drives: 8 hard drives various makes and ages (I just keep filling it up...)
    Graphics cards: 2 x Nvidia GT 450 (I use two simply to have different resolutions on each of two monitors, not for gaming or anything.
    RAM: 12 GB DDR3 average branded spec.
    Cooling: Corsair Hydro series H55
  4. Best answer
    OK. I'll have to get back to you later. But the INTEL CPU auto-throttles or shuts off shuts when overheating. Whatever caused the system to shut down is probably causing the fans and water pump not to run, so most likely their failure to run did not cause any heat damage. You have a lot of stuff in there, LOL! You might try unhooking everything incl. removing power from all drives and USB devices - nothing but one video card, one stick RAM, and power. Re-set CMOS and cross your fingers. See what happens.
  5. You're the best! Thank you for helping me.

    Ok, as I followed your instructions and removed som cards and things, I noticed that the light on the mobo was going on and off. As I moved that thick cable that goes straight from the PSU to a socket on the mobo, I noticed that it seemed a bit woobly. I moved it around a bit, detached and re-attached it, and voila, was able to get the fans to work.

    I had already reset the CMOS, so I will have to go in there and restore the settings, after putting all the bits back in the machine.

    I will post again when hopefully, everything is back to normal... :)

    Why that cable suddenly went strange without anyone touching machine is a bit of a mystery, but so far so good! What would you make of it?

    I will try to restore everything, and boot up again. Thank goodness, a computer failure was the last thing I needed right now!

    Thank you for speaking calmly and giving me sound advice!
  6. maybe the CPU AUX cable was just loose. sorry if the cmos reset wasn't needed. After you get the BIOS settings like you want them see if you can 'save' the settings in the BIOS menu so you won't have manually reset them if you need to do this again.
  7. All back to normal! :) ! Resetting the BIOS took a while, because I had OC:d and didn't remember my settings (this machine is now OC:d by 48% would you believe! I saved the settings though, so I'll be able to get it back quickly if something similar happens again.

    I was very near writing off the CPU because I believed it was vulnerable.

    Thanks again for the help!
  8. By 'saving the BIOS settings' I meant actually using the ASUS utility that saves a permanent profile which lasts even through a CMOS reset, not just 'pressing f10 to save and exit', if you know what I mean.

    I guess my instincts that this was power related were correct but I should have suggested checking your power connections instead of leaping to more dire scenarios - since the PC just suddenly stopped working I made a bad assumption that the connections would have been exempt. Glad your PC is OK anyway, and what Ghz does that overclock amount to?
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