PC Powering down problem

[Dark Sotonic Mills]

My desktop is playing up. I normally leave it switched on but this morning it had switched itself off overnight.

On restart everything started as normal, then powered off when windows had started but before all the desktop startup had finished.
Subsequent restarts resulted in powerdowns after an amount of time consistent with the time left between attempted startups.

Startup immediately, powerdown within a few seconds.

Leave for a few minutes, it goes for a longer tiome before powering down.

Now this seems like an overheating issue to me , but I have checked all the fans and they seem fine and I have made sure that all the vents are clear of dust.

Any suggestions how to diagnose the problem as sometimes I can't even get into BIOS before it powers down.

[mattbrennan]

Have you checked the power cable? Had a similar problem a few years back and it turned out that the power cable had just given up. Replaced it and it worked fine.

[Dark Sotonic Mills]

Managed to get it to stay on long enough to check the CPU temp in the BIOS. It went up to 192 then shut itself down.

Right, fans seem to be OK, so do I dismantle the CPU etc and clean everything or replace the fan?

Or is the CPU on its way out?

[Son of Bob]

Is the CPU heatsink sat firmly against the CPU?

If it isn't it'll power down virtually straight away. Take the fan/heatsink off the CPU and clean both sufaces thoroughly (preferably with an alcohol wipe) Apply some new heatsink grease and put the fan/heatsink back on, making sure it's clipped in firmly to the motherboard. That might cure it.

[St Landrew]

The fact that the CPU takes instruction, i.e. that the OS starts to load up, means that it is functioning, othewise the system wouldn't probably get past the POST. It does appear to be hugely overheating though. So, several things to check here:

1. Power cable - whether or not it is dodgy, swap it with the monitor cable, or another kettle type lead, that you're confident about.
2. The power supply may be spiking. I would normally just substitute to check, but I appreciate people don't have spares lying around, so you'll have to trust this for a while. Perhaps when you've checked other things, you can come back to this and minimise the strain on it by disconnecting devices like DVD drives, etc..
3. Fans and Heatsinks. The CPU heatsink and fan must be working absolutely efficiently. Check that you can feel a blast of air against your fingers when it is turned on. Make sure the heatsink is completely dust free. Here's where it is probably a good idea to have a basic check of the condition of these components, and to check on the state of the CPU itself. Have some replacement CPU paste standing by..! If the dismantling requires motherboard removal to release the heatsink, then it's probably a good idea to vacuum the heatsink and fan first to remove all the dust, and then check. If you get an improvement, then you can decide for yourself whether it's worth going the whole hog.
4. What is the temperature inside the PC box..? Is it cited next to a radiator..? Is it on the floor, and do you have pets and/or long pile carpets..? Odd couple of questions, I know, but they do add up. Check for clogged other fans, and their efficiency too.
5. Check the BIOS for advanced settings that may encourage excessive heat through work, or if you have a PC Health or some such area within the BIOS, check that the fans aren't being minimally powered to save energy.

Btw, DSM. Unless you have a good reason for leaving your desktop on all the time, I'd switch it off when not in use. There is an argument that all the heating up and down ages components, which is true, but nothing ages components like continuous work. And a PC that's turned off for 2/3rds of it's life is 1/2 the age of one that is turned on all the time. Without question, all the ancient computer curiosities [20 years and over] I've come across that power up without hesitation have had a damned easy life by being turned off when not needed.

As mentioned before, I do a lot of checking by substitution. Often it is easier and faster than getting a test meter out of its box, and a motherboard/other manual alongside. It could be one of several things, but if you just take logical steps, I'm sure you'll come across the answer.

[Al de Man]

Is the CPU heatsink sat firmly against the CPU?

Agreed. CPU heatsinks tend to be fixed under quite a bit of tension in four corners and if one corner isn't firmly fixed, the heatsink may appear to be in place but a gap will form between the CPU and the heatsink and it'll overheat in a matter of seconds.

Does it look a bit like this?


If so, give each of the four push-in connectors a wiggle and they shouldn't move too much.

[Weston Super Saint]

Managed to get it to stay on long enough to check the CPU temp in the BIOS. It went up to 192 then shut itself down.

Right, fans seem to be OK, so do I dismantle the CPU etc and clean everything or replace the fan?

Or is the CPU on its way out?

Don't discount the old S.M.A.R.T hard drive will turn itself off if it is on it's way out - had the same problem before and it registered excessive heat, but swapping the hard drive and everything returned to normal...

Curious things PCs.

Thanks all for your help and suggestions.

[Dark Sotonic Mills]

Sorted.

Took the heatsink and fan off and the thermal paste was dry. Not being able to find any at home I popped to Novatech to get some and decided to buy a new Arctic Cooling H/S and fan as well.

All now running at 12 C (53F) so am happy.