Why is MBP randomly shutting down? Thermal sensor? I/O, Logic Board?

Dear iFixit Reader,

my MBP 15inch late 2007 model A1226 2.4ghz has following story, in short:

The MBP has a 5 month old logic board and everything's been fine since the replacement.

Two days ago, while using it on battery it just turned off even though battery was at 80%. I tried turning it back on, MBP would fail after nimble boot attempts, maybe 1-2 seconds of booting, then shut off.

So I plugged it in the power connector and still no booting. I knocked it a slightly on the right side just below the speakers and it turned on... Right after logging in into my user account it would automatically log me out again, repeatedly, even in safe mode. Then I booted it up in my windows partition, everything worked fine there..

I decided to format the HDD and restore my MBP snow leopard from a 1 week old backup, way before any problems began. During the restoration process my MBP would just randomly turn off, without warning, just plain dead and no restart possible. A little more knocking and suddenly it restarted. Finally I got lucky and it restored fully, everything worked fine for about an hour, then disaster, it turned off again. Now knocking would have it either turn off when on, or on when before it would not want to start.

So I went to the Apple store, I had them run diagnostics and they don't exactly know what's broken but they believe its the thermal sensor and they want to put a new logic board in for a flat rate repair costing around 310 USD without tax.

However, when reading the description of what a thermal sensor failure looks like, it does not add up, there is no fan noise and the boot attempt is maybe 1 second without any screen activity.

What do you think is the root of the problem? What would you recommend me to do?

Thank you very much for your help!

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Thank you all for your quick responses.

The logic board was replaced because the NVIDIA graphics card burned through and that was covered by NVIDIA under production error extended warranty.

It takes 1-2 seconds to crash without being frozen. I live in high humidity Miami and I am afraid that putting it into the freezer would lead to condensation inside of the laptop... Also, the operating temperatures are declared by Apple to be way above freezing point.. should I worry about that or just put it into the freezer?

If its just connected without battery leads to same results, random shutoffs and then no restart... It shuts down with power in/out, battery in/out.

Thanks!

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What's happening if you use the MBP without the battery just connected with AC adapter ?

Looks like a power issue related to a bad connection somewhere since tapping the computer produce a shutdown. You should take off the top case and check the connectors on the logic board.

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I'll take it apart and take a look! Thanks for the advice. I'll keep you posted!

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Felix will be eternally grateful.
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