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Model A1312 / Mid 2010 / 3.2 GHz Core i3 or 2.8 & 3.6 GHz Core i5 or 2.93 GHz Core i7, ID iMac11,3

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CPU Fan on full speed

I have a problem where a CPU fan its spinning on full speed, in Macs Fan Control

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And its shows 0 RPM, but sometimes its shows some random values.

I had this problem and i ordered a new cpu fan from aliexpress, and installed, but after checking RPM status, the problem its still not fixed.

Does someone know what the problem?

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Not sure why you thought the CPU fan was the issue, one of your fan unit has failed. Within the fan is a tachometer which SMC uses to know the fan is working, if the tach fails the system will go into CPU safe mode which ramps the fan up and lowers the CPUs clocking to prevent if from overheating.

The best thing here is to run the onboard diagnostics to identify which fan is failing. Restart the system and press the D key to enter. Let us know what it tells you as well.

Mac startup key combinations

Here’s a listing of the iMac Intel 27" EMC 2390 Fans

Update (08/20/23)

OK I think found a similar case to yours Late 2010 iMac getting quarter way through booting then turning off

I’m not sure if the issue is a corrupted drive or the logic board has a deeper failure here.

SMC does interface with the North Bridge Chip so it’s possible it’s failure is causing Fan to be running hard and not correctly report it’s RPM.

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7 Commenti:

OP never said he thought the CPU was the issue. OP said that he thought it was the cpu fan


@diodeinc - sorry head was faster than my fingers! A fan has failed which one is the question! The point here was to run diagnostics to find out!


Hey,I'm run diagnostic program, and he's returned -3403D


@hermanyusha - What is the version of OS-X/macOS you are running on this system?

Can you give us the full message that error doesn’t make sense.


Version macOS High Sierra 10.13.6, the error while diagnostic (Pressing D) is -3403D, other messages don't have


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Herman Yusha sarà eternamente grato.
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