Need help; Toshiba L355 shuts down 28 seconds after power up. Fan or?




I'm working on a Toshiba Satellite L355, 2.2Ghz Celeron, 3Gb RAM.. i think they're all similar.
Anyhow, when I boot up the computer it shuts down in (almost) exactly 28 seconds no matter if i'm trying to boot windows or go into the bios settings... I took the whole thing apart and cleaned every piece and blew out all dust from the heat sink module and made sure there were no obstructions, however there is no change in operation.

The fan powers up with the computer but only stays powered for about 1 second before slowing down to a stop. I've cleaned the fan and made sure it turned okay and it wasn't making any strange sounds or anything. The area around the processor seems to get pretty hot in that 28 seconds before it shuts itself down.

Since I hate laptops and despise working on them, here's what i'm wondering:
* Is this normal for the fan to to turn on for 1 second on a boot and then turn off?
* Is there something wrong with this fan, or is the motherboard screwing up telling it not to run?
* OR is there some kind of problem with the thermal sensing (a thermistor or whatever laptops use)

I can order another fan for this thing, but the fan DOES spin when it boots so I was wondering if the
MOBO might be screwing up and putting a new fan it would have the same result.

If anyone has answers/questions/insight please let me know.
Here's what i've tried:
* Pulled RAM/DVD-ROM/Hard Drive, etc.
* Completely disassembled laptop down to the heatsink and completely cleaned it and the fan.
* I also did what I've heard of as a "static reset" where you pull the AC/Battery, hold the power for 60 seconds, etc. Did nothing.
* Reset the BIOS settings to default, even though they apparently already were default.

What this problem ISN'T:
* Something to do with windows.. it's not software... it dies in the BIOS settings as well.
* A battery or AC power problem. I've ran it without the AC, without the battery, and every combo
you can imagine.
* Fan obstruction... cleaned it until it looked almost new. Heatsink is perfect.
* To my knowledge, the BIOS hasn't ever been flashed, should be whatever came with it.
* No hardware has been installed that wasn't factory OEM that came with it.

This problem seems to be not entirely uncommon, but the fan thing has me stumped. If the CPU is
getting hot enough to feel through the case I'd imagine the fan should be on... but since it spins for a second on boot up and doesn't produce strange sounds, It doesn't seem to be normal symptoms of a dead fan.

I really though it might be a thermal sensor or a fried MOBO. But I really only know desktops..

- Chris. :fou:


If the fan appears to spin normally at start-up then the fan is okay. I would suspect the power supply circuitry on the mobo -- any funny smells ?


Theres no funny smells or obvious signs of a short in the mobo. The computer stays running for exactly 28 seconds, even if it's been started over and over. I would think if it was reaching a certain temp and shutting down then it would reach that temp quicker once the CPU had already been running. I just don't know much about how laptops deal with thermal issues.. I don't know if it's detecting the fan not running and shutting down, or that the CPU temp is too high. The BIOS doesn't show any temp or fan speed info.

Anyhow, does anyone know any good ideas to test the problem or fix this problem instead of swapping the MOBO? A new MOBO is like $150+ or something and it would barely be worth it in this computer.
Any insight is very helpful. Thanks.