Released October 2008 / 2.4, 2.53, 2.66, 2.8 or 2.93 GHz Core 2 Duo Processor

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Which fan is defunct?

The failure code according to the extensive (detailed?) Apple Hardware Test:


One of two thermal sensors seems to be malfunctioning. But how do I find out which one?



Here it is:

Last 4 S/N digits: B1GA

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Thanks for the hint: got Temperature Gauge 4.1 from the App-Sore: All fans are functioning normally at 2.000 rpm. I'll have to perform a total tear-down of the MBP to see whether there are any thermalsensors attached to the heat-sink or the main board.


Not so fast here ... There are multiple sensors. If both fans show they are running then you have a different problem. Can you give us the last four digits of your S/N so we can correctly ID which model you have.


Your system is: MacBook Pro "Core 2 Duo" 2.53 15" (Unibody) 2.53 GHz Core 2 Duo


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The best way is to download a temperature monitoring app like Temperature Gauge 4.1 Just make sure it calls out the different temperature probes.

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If the fans show RPM's and the temperature levels are not excessive I can't explain the AHT error unless something was jamming the blades and now for some reason is not jamming the fan blades. Open the cover does things look fairly clean or do you have a lot of dust buildup? Look at the logic board, the fan blades and the head transfer fins just in back of the fans. Over your desk turn the system over and carefully shake your system did a screw fall out (don't loose it!) or something else?


Thanks for your quick response, and I did as you suggested: tore the MBA apart, cleaned the fans and blades, brushed the dust off the mainboard, top and below, and other hard-to-reach-places, shook the nearly empty case for some screws or the like - and put everything back together again.

I can't complain, everthing works fine and the fans stay put. What takes me to the question: can AHT really be relied on?


I tend to run it a few times to make sure it's not a spurious error (or I failed to plug the system in). To be truthful here, I have not seen it tell me something was bad when it wasn't. Most of the time it doesn't catch problems, not report phantom problems like what you may have had. I still think something was jamming the blade (loose screw) which I've encountered a few times. If this answer answered your question please remember to score it & mark it accepted.


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jirudo will be eternally grateful.
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