Hi I have a friends Sony Vaio Laptop pcg-3c2l that is overheating and turning its self off. Fan will start as windows starts with a short burst then doesn't turn on again. Not sure if the fan is going out or the thermostat is going bad. Is there a way to check the thermostat and can you replace one on this model or should I replace the fan first to see if that is the problem.

How do you know that it is over heating? What are the temps?

I would start by opening every panel, and removing the battery and drives and, with a can of compressed dusting gas, blast out any heat trapping dust.

Yes I know it is over heating but haven't been able to get it to stay running long enough to get a temp reading. Have already cleaned out the dust really wasn't much. Have run it with the back off which lets it run longer but can't get to key board to check anything. You can feel the heat coming off the sink but the fan doesn't ever turn on then it shuts down.

Well, you could try blasting a desk fan in there. Note there is no thermostat in computers. There are heat sensors and fan controllers but these are not something that can simply be replaced. The fan can be tested by connecting it to another power connection - though that being a notebook, I doubt there would be a spare connection to try. It is most likely a 12VDC fan and if you have a 12V supply laying around, you could test it that way. It is pickle either way. If you buy a new fan and it ends up being the controller, you wasted your money on the fan.

If you can get into the BIOS, I would check the PC Health settings to make sure the shutdown threshold is not set unrealistically low.

Can get into the bios all the usually f-keys don't seem to work keep getting a scan of some sort but the computer won't stay on long enough to run it. Going to try swapping out the fan and see if it works. If it doesn't it is most likely the heat sensor.

You can't replace the sensor, so if that is it, about you can do is disable it. But that can be dangerous. You will have to monitor your temps carefully.

Any idea where the sensor is and how to replace it?

I'm guessing you missed my last post.