Late 2009 iMac problem

[yabush]

Hi all,

My iMac just stuck at gray screen one day after it hung and I forced rebooted it.

I tried to reinstall OSX, but once it rebooted, it still stuck at the gray screen.
then I tried to format the computer with the disc, the disc can be shown in startup. But when it was trying to load it, it then turned into some interlaced image (grayish and greenish).

I can enter the safe mode, but I wonder if it is normal if screen flashes once a while in safe mode?

From what I describe, what could be the problem of my computer?
harddisk or graphic card??

Thanks

 

[h9826790]

You can try to run the Apple Hardware Test.

Holding "D" during boot.

 

[GhettoMrBob]

I'd try what h9826790 said.

Since that iMac has discrete graphics I'd be sure to run that test and the memory test...sometimes funky RAM can cause errors like that.

 

[yabush]

I cannot launch the hardware test and I do not know why.

But I brought my iMac to the Genius bar a week ago.
They told me there's no hardware problems and had reinstalled the OS for me.
However, when I got there and tried to test it, the problem persisted.

Now they told me it's probably the problem of video card,
but after changing it, the problem was still there.
They suggested that it could be the problem of motherboard,
I am rather disappointed that they failed to discover the problem at this point.

 

[defboob]

My 27" 2009 iMac recently crapped out too - here's what i have discovered thus far on it, i was facing very similar problems like yours.

Originally I was using it one day and the OS just crashed, forcing me to restart. Upon restart is when I got stuck at the gray screen w/ apple logo upon bootup.

When I checked out the hard drive via the drive utility at bootup, it did come back with some errors that the utility was unable to fix. The iMac still worked in safe mode however, so i just backed up what I had on there and planned on getting a new hard drive.

I got the new hard drive, installed it - started the whole fresh OS X Mavericks install from a USB stick, and wouldn't ya know... the same thing - after the install the OS just hangs at the gray screen apple logo...

After searching more, i came across this help thread:

https://discussions.apple.com/thread/3263472?start=15&tstart=0

It turns out this was my issue - it was my ATI video card in the iMac - once I removed the ATI drivers from the system folder like the instructions in that thread, my iMac booted up just fine. The only downside of course is now you have an iMac with awful software accelerated video, which is basically un-usable. Basically my ATI graphics chipset in the iMac has crapped out, and now i'm stuck with a lame iMac.

What i'm considering now is turning this iMac into a nice 27" display for a new macbook - to tide me over until whatever new hardware comes out this Fall

 

[bmullemeister]

iMac problem

Hi I had similar problems and had 3 visits to the genius bar
They replaced the hard drive but the problem persisted eg all types of errors

I have 4 x 4 Memory chips and decided to take one out....luckily it was the faulty one and everything was fine again.
I replaced the 4Gb memory and have not had a problems since
Bert

 

[yabush]

The Genius Bar is still trying to figure out the problem.
If it's the problem of the ram, it would be easy, and I hope it's the problem with the ram.