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Apple Notebooks Apple's notebook computers including MacBook Pro, MacBook, MacBook Air, PowerBook, and iBook.

SMC has given up on fan control


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mystadobalina

 
Member Since: Sep 07, 2011
Location: Maryland, USA
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Mac Specs: Late 2006 2.16 GHz Core 2 Duo 15"

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My friend has an early 2006 15" Core Duo 1.83 with a serious SMC problem. After cruising the forums, I've gathered that this model is notorious for overheating. So here's how I've reached my diagnosis:

--She complains that computer gets hot and shuts down unexpectedly with moderate use of CPU
--battery cycles are dead due to unnecessary power usage
--After running CPU stress test and monitoring temperature, it read that her core was tripping shutdowns at 255 degrees F (123C!!), with no fan response
--Downloaded SMCfancontrol and tested fans, manually setting on 5,000rpms- system hovers around 215F (100C) on load, which is still not good
--reset SMC and PMU
--physically inspected fans for blockage or mechanical failure
--when manually setting fans at higher minimum rpm, fan speeds DO increase, but at a very slow rate and only tops out at 3,500 rpm at the core's hottest temp.

SMC IS communicating with the fans, but very poorly, and it would be a serious inefficiency to run the fans high all of the time. Any thoughts? Thanks

-mJ

OS 10.6.8
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harryb2448

 
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Sounds like it needs a good clean out. Dust is the prime enemy of all computers, particularly iMacs.


http://www.ifixit.com/Answers/View/1...tel+Core+2+Duo

Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!
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mystadobalina

 
Member Since: Sep 07, 2011
Location: Maryland, USA
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Mac Specs: Late 2006 2.16 GHz Core 2 Duo 15"

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Already checked fans for dust. While it could be they need lubricating, that still doesn't address why the fans do not respond to extreme temperature increase without manual instruction.

OS 10.6.8
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BrianLachoreVPI

 
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You're saying fans - plural. Is this behavior the same for all fans or just the CPU? It's entirely possible that you just need a new fan after 5 years.
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mystadobalina

 
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Both fans function at all speeds when manually set, but do not increase their RPMs automatically with temperature rise - that's why I'm ruling out a hardware issue, unless there is some SMC communication wire I don't know about that is loose or something.

OS 10.6.8
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chscag

 
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A machine that is 5 years old is probably going to experience getting warmer than one which is newer, however, those temperatures are unacceptable. It sounds like the temperature sensors are not working or the thermal paste on the CPU heat sink is almost gone. Either defect especially the lack of thermal paste will drive temps up quick.

Use the instructions at iFixit: The free repair manual to take the machine apart down to the logic board. Inspect the CPU area heat sink and the GPU to see if there is enough thermal paste left to provide the proper heat transfer. Also take a look at the thermal sensors to see if they're cracked. Not much you can do to test them though. Just have to swap them out.

I'm not sure if a machine that old is worth putting money into. A decision that the owner will have to make.
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BrianLachoreVPI

 
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Well- you really can't rule out HW based on the information you've provided. You indicate that the fans (you don't say which ones and I would be surprised if they were all behaving exactly the same way) respond to SMC control - but slowly and never exceed 3500 rpm in spite of being told to. You say they don't ramp up themselves at all - even if the CPU is baking. You're really only left with HW issues - but potentially 2 of them if what you're saying is true. Your temp sensors must not be working correctly, because the data paths for the fan instructions are fundamentally the same AND your fans must have some issues since they can't reach max speeds and respond very slowly. I think you're definitely looking at a HW issue - but difficult to say exactly what from here.
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mystadobalina

 
Member Since: Sep 07, 2011
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Mac Specs: Late 2006 2.16 GHz Core 2 Duo 15"

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Thanks everyone for the amazing insight - I'm pretty savvy with taking apart Macbooks, but I wasn't aware of the temperature sensing HW- I figured there was some internal component that could be the culprit with bad temperature communication, but I couldn't put specific HW to it-

now to get my hands greasy with thermal paste...

OS 10.6.8
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