Model A1418 / Late 2012 / 2.7 & 2.9 GHz Core i5 or 3.1 GHz Core i7 Processor

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Sensor Error After Hard Disk Replacement

After replacing the HD I receive this Alert from the Apple Hardware Test:

4SNS/ 1 / 40000000: TH00 - 9.000

Is this the thermal sensor of the hard disk ?

What I've missed ?

Giacomo

Answered! View the answer I have this problem too

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Here's a good reference on the AHT error codes: How to invoke and interpret the Apple hardware tests. While a bit dated it still works for most error codes.

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I have the same problem, 4sns TH sensor (Hard Drive Thermal Sensor), the fans running in 6000rpm and mac run very very slow.

Did you find one way to solve this problem?

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4SNS/ 1 / 40000000: T H 00 - 9.000

4SNS - System sensor

T - Temperature

H - Hard disk

As you can see yes the sensor within the HD is not active.

Did you replace the HD with a SSD or a HD? If not your system should still be covered under extended warranty. You'll need to talk with Apple.

If you swapped out your drive then the drive you put in does not comply with the newest SMART spec.

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I replaced a broken HD with a similar model (samsung momentus 1TB).

The Imac is no more under warranty support.

Curiosity: after replacing the HD, I needed to open again the iMac and replace the RAM also, the installation of the OS never went to the end.

After HD and RAM replacing the iMac worked normally.

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I think that all new HD are currently supporting SMART

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It's the version of SMART thats the issue here. Yes, all SATA drives offer some version of SMART services but over time it's been updated. About two years ago it was updated with a better internal temperature monitoring method which Apple championed.

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Get Macs Fan Control, it can be configured to use other thermal sensors to spin down the HD fan

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@giuliano - Giuliano, overtime we've learned using software is not that smart. The better direction is finding the root cause.

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@danj software is all that runs on a computer: it is not an electromechanical mechanism that changes the fans' speed... if Apple software cannot talk to modern drives, what's the problem in using software that does?

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@giuliano - Fan control software alters the systems SMC services which is what we don't want as over time it will cause a major failing of the system. The root issue here is the failure of the one of the SMC thermal sensors which needs to be fixed. Unlike the 27" model which uses a 3.5" drive the 21.5" model uses a 2.5" which uses a standard HD unlike the larger system which requires either the correct Apple HD or you need to get a special adapter made by OWC.

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