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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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Trying to identify why my iMac won't boot

My problem is that when I turn it on the screen has vertical bars and midway through the startup it gives an error message and restarts and keeps doing this.

I've tried the following things:

1. PRAM and SMC resets

2. Running hardware diagnostic test which gives "4MOT/1/4000003:HDD-1345"

3. Recovering from TimeMachine backup - same symptoms

4. Took glass off and front frame, checked the LEDS - all 4 light up while it's trying to start

5. Removed the LCD and gave everything a clean with compressed air, checked that fan that sits below optical drive is turning with power on

6. Lifted heat sensor off HDD and put it back on and retaped.

I'm dreading it is the video card since that looks more involved to get at but will try that if need be rather than just throw the iMac away. I could buy an adaptor to plug my DELL monitor in, would that help to confirm whether its a video card problem?

Any suggestions of diagnostics I can do to identify the problem please? If I could fix the problem I would go ahead and replace the HDD with a SSD and upgrade RAM from 4 to 6.

Thanks for assistance you can provide.

Edit: Photo added

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Edit: I followed the instructions iMac Intel 24" EMC 2267 Graphics Card Replacement and have removed the video card but no idea what to do with it now! Could I try baking it? I believe it's a NVIDIA GeForce 8800GT - G92 is it replaceable? I also took the HDD out for the heck of it but no idea how to establish whether there is a problem with it. I lack the diagnostic knowledge!

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Answered! View the answer I have this problem too

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@davidk64 - Sorry for not responding sooner I had thought @oldturkey03 had responded.

To start with you're going to need a new HD fan unit: Hard Drive Fan - Apple P/N 922-8154 to reslove the 4MOT/1/4000003 error.

For the lines on the display: You'll either need to try to reflow the solder joints of the GPU & VRAM chips in an oven (cheap toaster oven which you can't use for food afterwards) or replace it: ATI Radeon HD 2600 Pro, 256 MB - Apple P/N 661-4426.

You'll also need to clean off the old thermal paste and pads from the chips and refresh them with new paste & pads. Apple also tried using a gapping thermal paste on some boards on the VRAM chips. I have found the pads are better. Here's what I would use:

Then you'll need to use a feeler gage to figure out which sized pad to use it needs to be just snug.

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@danj Many thanks for the reply. I delayed responding awaiting delivery of thermal paste from Greece. Have baked the card and that has fixed the vertical lines. The machine boots up fine now. I ran the hardware diagnostic using the original OS disk and got the same error for hard drive fan. I have ordered a replacement fan using the link you provided but will have to wait for delivery from US. Will let you know the outcome when it's installed.

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Where are you? on an island off of Greece?

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The gapping paste is not as good as the pads.

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Just to say the replacement HDD drive fan arrived and after installing it and running the hardware diagnostic test shows no problems. Hopefully I'll get a good run out of the baked graphics card! Thanks @danj for your help. Very satisfying to fix (atleast temporarily) the iMac problems and get extended life from it.

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@davidk64 4MOT/1/4000003:HDD-1345 is an error code from the fan motor (MOT) on your HDD. Could be a failed drive, a faulty sensor or a failed fan. I'd start with trying to fix this issue first since it does explain some of your start-up errors.

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So one of failed drive, a faulty sensor or a failed fan could give the vertical bars? Any ideas on how I narrow it down to one of those three possibilities? If I knew it was the HDD I'd gladly buy a SDD and put it in but don't want to go down that path if it's something else that I can't fix.

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@davidk64 can you take a picture of your screen with the vertical bars and paste it here for us to see. Also have you tried connecting an external monitor to see if the bars are present on it as well Adding images to an existing question

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@davidk64 it would be uncommon but Apple has a thing for uncommon things to happen. You'll have to look at the HDD anyway so I'd start with that and work my way up. The HDD will be easier to manage than he alternative which could be the video card etc....

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@oldturkey03 @danj Thanks for the help! Have added photo. I've ordered an adaptor so I can plug in an external monitor but it'll be a week or two before it arrives. Is the fact I can't boot from my Time Machine drive or the original OSX install disk indicative of anything?

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David Kilpatrick will be eternally grateful.
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