Weird laptop temperature sensor problem

[Trann]

I have an IBM Thinkpad T42 laptop, it's just over 2,5 years old (3 year warranty).

Ever since i got it, it's been freezing randomly on me. It's always the same pattern.

With a fresh windows install (like when i got it new) it's fine, each month it starts getting worse and worst, down to the point it starts freezing 2-3 times PER DAY.
Then i reinstall windows, and it repeats itself again.

Now mind you, i'm no idiot with computers. I'm a Com-Sci graduate and i live by the rule of not installing crap that i don't need on my computer. I take extreme care of not having annoying trash or worthless services running in the background. I also always run the latest drivers and bios.

The freeze is definetly a hardware one, the computer completly locks up, doesn't matter wether or not i'm working in it, in fact it more often freezes when i'm not using it(allthough i have no screensavers or power-savers or anything like that enabled, so you can rule that out). No bluescreen, just plain old "num-lock doesn't lite up when i press it" freeze.

So, with it going out of warranty soon, i figured i might try to get to the root of the problem and maybe getting it fixed finally, if possible. So i started doing some extreme testing.

Now check this weird behaviour out.

It's probably like 25°c in my room right now, and about -10°c outside (i live in iceland).
CPU Temperature is 46°c according to speedfan(which is NOT set up for throttling). Been browsing the web on my dekstop for a while.

I put the laptop on my bed, and covered the exhaust, and put on some quake 3, and let it run at 100% cpu for a good 20 minutes.
20 minutes later, the cpu temperature is still 46. It hasn't changed one bit.
So, in the process of removing the laptop from the bed, i accidently remove the power coord (the coord is a bit bugged, it comes loose really easily now, you barely have to touch it), and instantly the CPU temperature jumps to 89°c!

Next thing i do, is i put it in the windowshelf, and open the window(it's -10°c outside), in the process i accidently pulled the plug again, so the temp is now 75°c. I let it run (with q3 turned off now) in the window, for a good 15 minutes. Temperature is still 75°c. The instant i touch the power coord it drops to 45°c.


So.. It seems that my computer only updates the temperature when it looses or gains power. Which could seriously affect the motherboards ability to monitor the temperature and control the fans accordinly.

Now ofcourse, this could be a speedfan bug, but it seems like a logical explanation to all of this.

But, if my conclusion is indeed right, how on earth could this be software related? (ie it fixes itself when i reinstall windows.. )

Quite weird.. I really don't know what to do. I'd feel like an idiot bringing my computer in for service with the description that it "freezes a lot".

So.. any input on this situation?

 

[Joe42]

Hmm, you wouldn't be the first person to send a laptop back under warranty for freezing a lot, so i wouldn't worry too much about doing that if all else fails.

First thing i would do is boot into a copy of knoppix and see if it freezes in that. This eliminates windows and more importantly the windows drivers. Its surprisingly easy to do, i know nothing about linux and i managed.
The problem i was having was a laptop was getting a bsod no matter what i did, for me it turned out to be a dodgy windows recovery disk, that's not uncommon. If you have another copy of windows try installing that.

I know in my laptop the heatsink is fairly easy to reach, can you get a temperature sensor on yours somehow perhaps?

Really if its under warranty it shouldn't be up to you to fix it, as long as its causing problems consistently you should just send it back and get it replaced or repaired. And if for some reason you can't do that then start messing with it yourself.

You can always try the usual bunch of stress tests, memtest for memory, sp2004 for cpu and rthdribl for gpu, see if you can consistently get it to freeze.