Faulty CPU temperature sensor

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Level 1

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Faulty CPU temperature sensor

Hello,

I am sorry if this is covered already in another topic.

Today I went to the local Apple service center to give my MacBook Pro 15 (OS ver. 10.6.8) for maintenance cleaning and a change of the thermal paste of the CPU. I got a call a few hours later and a technician told me I need to change my mother-board, because the heat sensor of the CPU gives incorrect temperature and the FANS start spinning at 6200 RPM without the processor to be loaded so much. (The price was too high ofc)

Well I know that if I start a graphic software or a game then the temperature and the fan speed rise but thats perfectly normal and logical. Though I have seen it many times the moment I start a game, temperature softwares like: Fan control or IStat Nano show around 30 or 40 degrees increase for just a few seconds which is not possible. And vise-versa the moment I turn off a game it drops to 50 or below degrees. I tried something else - turned on the laptop after it was cooled down to normal room temperature and started - Parallels Desktop /Windows XP then Heroes of Might and Magic V and loaded a saved game without actually doing something, just to check the sharp increase of the CPU temperature...it shows 108 degrees, though the body of my laptop was perfectly cool (where the CPU is placed). I think is impossible to generate such heat in just 2 seconds. The interesting thing is that the moment you stop it it drops to 45 degrees.

Please advice if you have any ideas. I can not afford to change my MB at the moment and the laptop guarantee has expired 1 year ago.

P.S I was thinking to increase the upper threshold of the Fan Control (now is set to the default of 80), though I am afraid to speculate with this...

MacBook Pro, Mac OS X (10.6.8)

Posted on Jun 30, 2011 7:02 AM

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Answer 1

Lexiepex

Level 6

14,108 points

Jun 30, 2011 7:24 AM in response to Psychoscotch

Solution may be on this site:

http://kb.parallels.com/en/111541

(if this anything to do with you using Parallels Desktop (which is a great App, BTW).

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Answer 2

Psychoscotch Author

Level 1

0 points

Jun 30, 2011 7:51 AM in response to Lexiepex

Thank you for your reply. I tried it under coherence mode though the result was the same; fans to 5900 + and temperature 100 and rising.

My main concern, despite the unpleasant noise coming out of the fans spinning at 6200 RPM is if I continue to use it this way (running on this RPM for a few hours) I would damage the hardware or shorten the life of the fans considerably.

P.S BTW for a test I checked World of Warcraft under Mac OS, no parallels/windows. The situation is a bit different - it goes to around 75 - 80 degrees

with fans around 5400. I forgot to mention that I use a cooling laptop pad as well.

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Answer 3

Psychoscotch Author

Level 1

0 points

Jul 5, 2011 5:47 AM in response to Psychoscotch

I would really appreciate some more comments if possible.

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Answer 4

Lexiepex

Level 6

14,108 points

Jul 5, 2011 9:26 AM in response to Psychoscotch

if you say 75-80 degrees, I assume Celcius. That's not very hot at all, especially with games. 100 is on the hot side, but when too hot it will shut down. Set the Parallels Configure VM as mentioned in the article in the link above. Use Window or Full Screen. In the meantime there is an update of Parallels but I am not sure if that has solved the problem.

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Answer 5

Jul 6, 2011 3:37 AM in response to Psychoscotch

Incorrectly applied thermal paste and heat sink attachment can easily result in very fast cpu temperature increases. With no heat sink in place the cpu heats so fast that it won't complete startup before it force shuts down. Replacing thermal paste is not a normal maintenance item. If it was done properly at the factory it never needs to be done again. Your system needs to be evaluated by a professional that knows what he is doing.

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Answer 6

Psychoscotch Author

Level 1

0 points

Jul 7, 2011 1:22 AM in response to Psychoscotch

Thank you both for your comments.

The dock it does not use a lot of CPU% in my case and when I use Parallels I use it in full screen without sharing windows applications.

My question though is how long is it reasonable to use my mac when the fans are spinning at 6200 RPM or a bit lower and my CPU around 100C?

As I mentioned I am not quite sure my CPU reaches 108C (as it shows on IStat nano) when playing Heroes of might and magic or any game under Windows using Parallels 6. (Playing games under Mac OS shows that the temperature is slightly less - around 90C).

Many thanks

P.S. Regarding the maintenance I went to a Apple certified service, I hope they didn't screw this up.

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Answer 7

Jul 7, 2011 3:25 AM in response to Psychoscotch

If your cpu tries to exceed it's maximum rated temperature it will immediately shutdown (crash).

Just because you have Parallels at full screen does not mean that other applications stop running. Everything that was running before you went to full screen for Parallels continues to run in the background.

Graphic intensive games can put a very large load on the cpu. They can also draw power from the battery while using AC power.

Your fans should be idling (2000 rpm) when the temperature is less than 70 degrees C. Somewhere between 70 and 75 C they should begin to speed up. A 100% sustained load on the cpu will have the fans at maximum rpm as long as the load continues. If your MBP can handle this sustained load without shutting down the heat transfer from the cpu is correct.

It is very unlikely that the temperature sensor for the cpu is bad since it's part of the cpu chip.

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