Does not compute.

September 24, 2008 1:25 PM

Computer/ Heat Sink filter: Why does my computer turn on for a few seconds then shut off?

After a long study session during the night I realized my motherboard fan was way too loud and needed a good dusting. After cleaning the damn thing I turned my pc back on only to have it shut off a few seconds later, and every attempt afterwards results in the same thing, just shuts off.

Everything looks and boots as it should on the monitor except for the fact that it shuts off.

Help! I need my PC back ASAP for school! BLEH!

Also if it makes a difference

Motherboard: MB MSI 945P NEO3-F 945P 775

CPU: CPU INTEL|P4 640 3.2G 775 2M 90N R

posted by Wanderlust88 to computers & internet (10 comments total)

Did you check to see if the fan is turning after the dusting?
posted by lee at 1:32 PM on September 24, 2008

How did you clean it?

Is the fan spinning ok when you boot up? Is it possible you disconnected any cables while cleaning the motherboard fan?
posted by demiurge at 1:34 PM on September 24, 2008

Try wiggling the heatsink on the processor. If it's a little loose, take it off and add some thermal grease to it, then replace. Also, consider a big after-market heatsink with attached heat pipes and a fan. Check out the Zalman brand. They've got lots of models depending on how much space you have in your case.
posted by spikeleemajortomdickandharryconnickjrmints at 1:38 PM on September 24, 2008

Get a stopwatch, a pencil, and some paper. Allow the PC to cool for a few hours.

Turn it on and time the amount of time until it shuts down.

Turn it on and time the amount of time until it shuts down again.

Repeat and repeat and repeat.

If the times are getting shorter and shorter, this can be one of two things: 1) It's a heating issue. 2) It's an issue where charge builds up and then reaches a critical point. This second issue means a troublesome capacitor. Do not laugh, this has happened to me. You won't know until you rule out the first option, typically by putting the PC somewhere cold (but not wet) and seeing if that doesn't increase the time to shutoff. If that time increases, it's #1. Otherwise, it's #2.

If the times are not getting shorter and shorter, it's a connection issue.
posted by adipocere at 1:50 PM on September 24, 2008

1. Yes the fan still turns(and as far as my naked eye can determine it looks like it spins at the same rate)

2. I cleaned it with q-tips and blowing on it

I will try to time the stopwatch trick and get back
posted by Wanderlust88 at 2:00 PM on September 24, 2008

It could also be a power supply problem. I was having similar problems and replacing my power supply fixed this.
posted by pombe at 2:17 PM on September 24, 2008

I second adding thermal paste. The paste may have hardened over time and then cracked away from the heatsink when you were cleaning.

Your local computer store has thermal paste for $1, and Radio Shack has it for $7.
posted by blisterpack at 2:35 PM on September 24, 2008

I should add, chiming in to pombe, that the bad capacitor in one of my two cases was in the power supply.
posted by adipocere at 2:54 PM on September 24, 2008

If it's just a "Few seconds" (five or fewer) from a cold boot it is almost certainly not a problem with heat transference (fan, heat sink, etc). That's simply not enough time for it to get hot enough.

That and virtually all modern CPUs will not shutdown immediately when it gets hot, it will simply underclock its self to keep cool. When you say "Everything looks and boots as it should on the monitor" what is it showing, how far into the boot process do you get?

I'd guess you probably knocked something loose. Open it back up, check all of the connection, make sure you didn't bend a header pin or drop a screw in there somewhere. Reseat all of your cards and any connectors that you feel comfortable touching.
posted by Ookseer at 4:18 PM on September 24, 2008

I'd try reseating the RAM, video card.

Also try setting the jumper to clear the CMOS.
posted by wongcorgi at 4:51 PM on September 24, 2008