MacBook Pro 17 shuts down without warning

Question

My MacBook Pro 17 inch shuts down without warning, usually in the morning. Entire systems simply shuts off. It will do this 1-4 times in the first two hours (or so) of operation. It restarts fine afterwards, but no telling when it will shut down again. Sometimes the fan powers up to a high speed just before it shuts off ... in seconds ... no time to "save" anything I am working on. Once the machine has been running for about 2-3 hours ... it stays on the rest of the day. It is still under warranty but I can't be without my system for more than a few hours. I have already updated the firmware that was offered as a fix for this at Apple support, no help. I am not running on the battery, plugged in all of the time.

Answer 1

Nothing shows up to be wrong during the diagnostics. A friend who is a PC guru told me what might be happening. He told me to shut down my system before it normally turns itself off. He said that an internal temperature sensor might think the computer is overheating and shutting it down to protect the processor. Makes sense, especially with the fan powering up just before it shuts down. So far, although inconvenient, this is working. He said shutting the system down might reset the temperature sensor. Seems to be working which might mean that some sort of internal sensor is defective. Time will tell, hasn't shut down for over a week now. I posted this in case anyone is experiencing the same issue.