iMac 27" 2009 Graphics problems

Here in the US, it was $192 for the replacement card, plus $39 for labor.

$231.04 total excl. tax.

Recently had our 2009 iMac (27") repaired after encountering these same issues - horrible graphics artifacts, Safe reboot ineffective, random total freeze & increasing frequency of self shutdown. Apple store didn't want to work on a machine this age, so local Authorized Apple substitute was consulted. It's getting a little harder to find replacement video card at low/reasonable cost, so they performed "reflow" (resolder existing connections with more and better material). They claimed that during diagnostic testing, critical components of video card, while quite warm, did not overheat. This indicated to them that a new card was probably not needed.

The repair work, including diagnostics, cost about $180. I'm a little skeptical, but everything is working well right now. We'll see how it lasts longer term (crossing our fingers).

NECROBUMP!!!

Alright, so I was having all the symptoms being discussed in this thread. Having worked on Xboxes a lot (and as a user above said), I figured the GPUs solder points were disconnecting so they would need to be reflowed. Since I could not find a guide for an iMac and aiming a heatgun at this computer is not a top priority, I figured I would try fix the issues the hobo way (see towel trick for Xbox)

So basically, the computer would have grey streaks then a box of black pixels in the bottom right corner after booting. Leaving the computer at this screen for a while got it really hot, then it booted fine. When this happened again and the fix worked again, the problem was obvious.

So, I booted into Windows and played sauna. I installed Macs Fan Control by CrystalIDEA (amazing program, fixed my issues of full speed HDD fans after non-Apple HDD replacement too) and found a game that would work. Settled on State of Decay. Launched the game, set affinity to core 3, priority to lowest and set the ODD fan controller to min 75 and max 85 (Celsius), minimized the game and put up with Windows for a week. Let the computer run 24/7 with the GPU diode averaging about 78 degrees and it seems fixed!

Yes, I know it's not a permanent, or particularly efficient, fix, but it's been fine for a month after the torture and it is free!!

Just my 2 cents on the issue.

27" 2009 with a 4850

i thought the graphics was on board, not a separate card ... please clarify since I am looking to purchase a used one of these iMacs. Thank you