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I have seen the same question posted on this site. I am at my wits end. My laptop will only stay on when I place it laying on the back of the screen with the key board straight up--weird?

I have taken it apart and cleaned the heat sink, the fan and even bought an external fan--same issue. I have tried the battery out with the power plug in the wall. All same results.

Any ideas?

Jan...Poland

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5 Answers

There is a sensor on most laptops that senses when the lid is closed. I have seen that sensor fail and it leads the OS to believe that the lid is shut and so it does what the OS is set to do.

Some of these are small pins that stick up near the screen while others are optical.

Check your manual for the location of the sensor

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I've seen some that are magnetic too, and they work like the sensors in most flip phones and also the sensor in the iPad2 that detects if the cover is closed. –  TuxRug Jun 3 '11 at 14:00
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I believe I'm experiencing the same issue as you. In response to the other answers referring to the settings for your lid being closed, I am assuming that is not the issue. With my laptop, I have specifically turned off the option for turning off when the lid is closed and I STILL experience this problem.

I would say you've taken the right approach so far with cleaning the dust out and adding extra ventilation. I think heat may still be the cause of your problem. Try downloading one of those free programs that monitors the temperature of your CPU. Keep an eye on it and see if the temperature increases dramatically until it shuts itself off. I did this and I saw that my laptop is hitting over 170F right before it crashes out, so I'm assuming I need more cooling options.

Can anyone recommend a good free CPU temperature monitor?

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I have seen the same problem in an HP 17" workstation (2.93 GHz Lynnfield processor) and an Acer Aspire 4730Z 14" laptop. I get a non-specific power failure error log message (possibly a thermal shutdown?) and it usually occurs with multithreaded makes. I can avoid the problem by exposing the bottom of the laptop to a window unit air conditioner.

I have no fix for the HP, but the Acer problem went away with the latest (1.22A) version of the BIOS. A multithreaded make on the Acer that took almost exactly 10 minutes on the 1.15 version of the BIOS now takes between 12 and 13 minutes, but never seems to fail any more. I think the new BIOS may be enabling memory throttling (since the hot spots on the bottom of the laptop are where the hard drive and the memory are located).

Good luck!

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Try turning off the setting in your OS to shut down when the lid is closed. On Vista, it is in your power options, after change plan.

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Take a magnet screwdriver and move it close to left hinge near joint, compare how magnet reacts to other places in lower part of screen. If you will notice that there is other magnet hidden inside laptop, then it is the one for close lid sensor. This is some stupid design with poor parts. I know that it is stupid because they usually put lid magnet next to speaker magnet and they stay in conflict for few years and eventually turn the fields. Aparently engineers who design lid and who design speakers placement work in different departments. They should trash this patent and forget about using magnets for lid sensors.

So the problem is that somehow hall sensor thinks that lid is opened only when laptop in some weird position. The magnet possibly demagnetized or changed field direction inside the lid.

To resolve it, try to set operating system to do nothing when lid is closed.

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