Q: Late 2006 iMac, Lines, Kernel Panic, Freeze, Reboot, Restart, Serial W8 ?

I have the same problem with my imac 20" 2006. I understand the heat & graphics issue but I have noticed a strange thing. If I start my imac in target mode (press t at start up) and have it connected to my mac mini firewire, the screen seems to work fine in target mode and the drive is available. Made me think is it the graphics card? Why is it working under target! I don't know if it's the graphic card after that but I do believe it is a heat problem. It works in target mode so not sure if it's hardware or software based.

Yes because in safe mode or target mode the graphicscard is not used.  If you disable the graphicscard your imac will work without all the issues.  Unfortunately movies and stuff that requires the graphicscard won't run without one.  All  the rest works fine.

I can't find the link to the article on how to do this but basically look for ATIRadeonX1000.kext and move that file to some other location and reboot.  Your graphicscard will stop to work and all issues will be gone.

It's hardware if you heat up the gpu causing reflow of the soldering it also goes away but that's a bit more drastically.

The good days are over.  After several weeks with no problems–after a thorugh clean up of fans and repasting of the GPU, the iMac is back to its bad behaviour.  The summer heat isn't helping either. Now, as I posted before, I don't see the fans ramping up as the tempearature increases inside the iMac, any advise?

It's 86 degrees inside my house (no air conditioning). I'm getting some relief for the Mac by turning a table fan on its exterior, and also using Fan Control. With this, I can keep the Mac internals at around 119 degrees, and it won't hang unless I play a YouTube video or use Google Streetview. Fortunately I don't have to Photoshop anything at the moment.

I have spoken to an Apple engineer about this and it's the graphics card.  Apple won't do much about it since my iMac is 6 years old.  I asked them to get me a cheap replacement logic board but the cheapest would be around $400.  The logicboards you find online range from $270 to $500 so that's not much help either.

The only thing that helps is to disable the graphicscard

This helps: http://www.canmusaogullari.com/2010/08/macbook-pro-with-ati-radeon-x1600-display -anomalies/

I removed : /System/Library/Extensions/ATIRadeonX1000.kext

Now the graphics card is not used, so a few things don't work well, like some videos but 90% works fine for my needs.

No crashes in more than a month!

The ultimate fix seems to reflow the solder on the GPU by taking everything apart and heating the GPU up till the point the solder starts to melt than to cool it down again.  This seems to work for a couple of months for some.

I did a reflow but it didn't help, I probably didn't do it correctly.  I'm gonna try to put it in the over at 200° C for 10 min.  and see if that helps.

Or I might just wait until I can get a cheap replacement logic board.  Anyhow the late iMacs 2006 with onboard graphicscard are not gonna be supported on Mountain Lion so you might be better of buying a new Mac.

same here. i tried the smc fan control and reaplying thermal past with no luck. any chances of an apple recall for defective product? it´s quite clear that it is a production failure.

On a 6 year old computer....chance would be a fine thing!

well, it seems a similar problem the santa rosa macbook pro had. they replaced the logic board for free no matter it was on warranty or not. i guess this one didn´t had so much press as the nvidia failure.

Add me to the list. Ive paid for 2 graphic cards & a seagate hardrive to be replaced so far on my imac. 2.16 Ghz Intel Core 2 duo 2gb 667 Mhz DDR2 SDRAM . Started when streaming live football the screen went crazy then frooze. Sent in repaired new graphic card. Then it happened again within' a year. Then the internal hard drive went. Been ok since mined. But now my wifes imac started playing up as well.

My 24" iMac (QP7070...) has similar problems.  About a year ago I was having  Firewire problems with my 2011 27".  While talking with AppleCare,  I mentioned my Firewire and horizontal line problems that I was having with my "older" 24" iMac.  Eventhough AppleCare on it had long expired, they volunteered to replace the logic board on the 24" for free.  However, about 6 months ago the horizontal line problem began to re-appear.  Now between Panics, and constant lock-ups (can only shutdown by using the back button) the machine has almost become unusable.  When I get it to run, I can look at my emails for a few minutes, but many times when I am half way through an email the machine locks up.

Something has to be wrong with there logic or video boards.  Now I wonder what will happen with my 27" once it is no longer covered by AppleCare.  It has already had its logic board and hard drive replaced. 

When it comes time for a new machine I am not sure what I will do.  The iMac is a nice machine when it is running, but not being serviceable at home, make it financially unacceptable due to the cost of repairs. 

I bourght a new imac in 2009  as a replacement for my 2006 imac having this problem. Got fed up with replacing everythink apple said was wrong with it hard drive graphic cards etc. Got nowhere with finding out the real problem. All i use the 2006 imac for now is a itunes jukebox for my mp3 collection.  GUESS WHAT THE 2009 imac has started behaving the same.  https://discussions.apple.com/thread/3938355?start=0&tstart=0

I've had these very same problems, did the Hardware diagnostic, repaired permissions with Disk Utility, had Apple store do its test — passed everything, but experts suspect a bad graphics card.  As a last resort, I did a simple cleaning — took my shop compressor and with a narrow nozzle I blasted a very strong stream of air up through the bottom vents (kept at it for 15 minutes) and in through the vents at the middle of the back.  Held shop vac at the top vent in the back.  I'm amazaed; so far it's now working perfectly and has for several days.  I dunnnnoooo, but its a very inexpensive thing to try.  BTW, mine is a 20", circa 2006 iMac with the Radeon x1600 graphics card.  Oh, forgot to mention that I downloaded the Fan Control appliction; it did nothing to help.

Hello

My iMac 24"/2.33GHz (you've guessed it; late 2006)  W8639 is suffering from exactly the same problems and has been for the last 12 to 18 months. I've been in touch with Apple and was basically told that they'd not heard of the problem. I also contacted a local Mac dealer who said the same thing.

I've been a Mac user (and advocate) since 1990 and this is the first time I've had one I can't rely on. Sadly Apple's blank refusal to admit to a manufacturing default in this model leaves a very unpleasant taste in the mouth, particularly given the number of reports of very similar problems.

I realise large companies are generally reluctant to admit to this type of problem because of the possibility of having to replace faulty products, but surely the reputation of Apple as a manufacturer of reliable computers and Mac users' brand loyalty is of greater long-term importance?

Totally agree.