General discussion

MacBook Pro fan runs hi when asleep

MacBook Pro 2.16 Intel Core2Duo with 2 GB 667MHz SDRAM runs very quietly when being used. When left with lid closed overnight but still logged in, each AM the the fan is running loudly at high speed and the case is hot. As soon as I open it and it starts up, the fan quiets down and the case is cool in a few minutes. The temps range (when open and quiet) from 90-125 F for various components and the fan speeds are about 2000 RPM. Why should it run hot when closed and asleep.

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First thing I'd do

First thing I'd do is reset the SMC, which may just have its signals crossed a bit. If that doesn't work, make sure you don't have anything like smcFanControl installed. That program may be useful in a limited number of diagnostic applications, but it shouldn't be used regularly. It can lead you down a dead end road when trying to sort out problems. So make sure any programs you have only monitor fan speed, not control it.

I'd be surprised if resetting the SMC doesn't solve it, but if it doesn't, then I hope you have the Apple Care plan on that system, because you probably have a logic board on its way out. That will run you several hundred dollars, and usually isn't economically worthwhile. Why spend $500-$600 to repair a system when for $1,000 you could get a brand new one, with better specs, and a one year warranty to cover these kinds of repairs?

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Many thanks

Reset the SMC (shut down,unplugged A/C, removed battery, held power button down >5 sec.) Replaced battery and A/C and restarted. Since this is my wife's laptop and it was only noticed when asleep for a long time, it may take two weeks to find out if problem solved as we are on our way to Calif.

Will let you know as soon as we know. Will follow your advice if it fails.

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Seems to me the simplest solution is to shut down the MCB when you are not using it. Don't let it run all night. I had a similar experience with a Sony laptop getting hot when the cover was closed but it promptly cooled down when the cover was opened.

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Except that isn't really a solution, more of a work around. Better to figure out why it's doing this, and fix it if possible, because it shouldn't be happening. When you close the lid on a Mac laptop, it's supposed to perform a suspend to RAM operation, so only a minimal amount of circuitry should be active and generating heat.

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Ok for two days

After resetting the SMC, the fan was quiet in the AM for two days, then started up again. I reset the SMC again but with traveling have not been able to recheck it again. I do shut it down while traveling.

If it is the logic board, what do I expect? Can it work for an extended while? If it fails, is the data recoverable without too much trouble? What other problems are likely to show up with a failing logic board?

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It depends

It depends. Excess heat can damage things in an unpredictable way. You may go for years without seeing any signs of damage, or the whole thing could just decide it's not going to boot anymore tomorrow. There's just no way to tell.

If it ends up being the logic board, I'd just shut it down when not in use, and use the thing until something else fails. Unless it's under warranty still, then take it somewhere to be fixed. Repairing a bad logic board is pretty much never economically sound with it being 60-70% of a new system.

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Thanks again

Appreciate your expertise. Will hope over the next few days while traveling that the second SMC reset was more successful.

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