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Model A1225 / Mid 2007 and Early 2008 / 2.4, 2.8, or 3.06 GHz Core 2 Duo processor

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Will not boot or restore, but I can install and run Windows!

Hi people,

I'm repairing a 2008 24" iMac 3.06GHz, and see these issues:

Booting anything Apple, it freezes on the grey screen with the Apple logo and spinning wheel, halts about 1/4 through and the either just sits there or restarts.

Booting anything does not work. It will not boot OS X, Safe Mode, recovery partition, from a DVD or from USB.

However - I can pop in a Windows 7 DVD, and it will install and run great (!)

It will display the boot menu (hold Option key), and I can see the internal disk, the DVD in the drive, and all connected USB/FW disks.

It will start up in FireWire target mode, and I can see the internal drive from my working MacBookPro via FW.

If I put my MacBook into FW mode, I can see its disk via FW on the iMac, but trying to boot it gives me the same result as above.

Actually, the iMac has just corrupted my otherwise working MacBook HD, so I am recovering that machine as we speak...

I have replaced the logic board and the RAM sticks (confirmed working on another Mac that uses the same kind of RAM), tried another hard drive, but nothing helps.

The super-weird thing is that I can pop in a Windows 7 DVD, and it will install and run flawlessly.

So this tells me that the logic board, the display and graphics card and RAM should be working.

I have done PRAM/SMC and all that stuff.

Answered! View the answer I have this problem too

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No one ever heard about this? Any thoughts?

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hi there, check what show the diagnostic led's

iMac Intel 24" EMC 2134 and 2211 Diagnostic LED's

did you look for some faulty sensor?

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Hi, yes I did - all the LED's are on (green) when the iMac is on.

Faulty sensor?

It is missing the temperature sensor for the internal hard drive, which probably is what causing the HDD fan to be full on all the time... Could it be that simple?

But how would that explain that I can't boot from a OS X DVD, but can boot from a Windows 7 DVD and install and run it?

Is it possible that OS X will kernel panic with the lack of a HDD temp sensor, but Windows will run fine?

Thanks for replying :)

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windows is not made for imac but for all pc, he don't care about the sensor.

so can be possible some issue trying boot os without the sensor....lets try

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Yeah I know it's made for pc's, but since it is Intel hardware, it can run Windows perfectly fine, independently from OSX.

I agree with you that the missing sensor might be the problem, since OS X looks for it, and Win does not. Maybe, if it thinks that the HDD is overheating, it crashes... I don't know yet.

Well I don't have a new sensor at hand, so I need to order one first.

I have found Apple's Service Technician's Manual for this machine (and a lot of other Macs), and it contains valuable troubleshooting info. It mentions resetting the logic board by removing the CR2032 battery for a few minutes.

I'll come back here with updates :) If anyone has any other thoughts, let me have 'em :)

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Ordered a new sensor - on it's way from eBay.

I've read elsewhere that you can just short the connectors on the board, and it should take care of it... Later.

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You know what, I think it might be the graphics card - booting the OSX install DVD in verbose mode shows a freeze when loading the gpu kexts.

Found a very cheap 20" iMac from the same year, gonna use it as donor for this.

Updates will come...

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Jakob will be eternally grateful.
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