iMac Freezing and having Display Issues - Overheating?

I'm having (and have been having for a couple of weeks) some issues with my iMac 9,1. I'm running OS X 10.6.8 and I'm experiencing the computer freezing, though the mouse still works. I've run Apple Hardware Test twice and just did the TechTool Deluxe test. Both couldn't find anything wrong. I've also checked the Console Log and none of the reported errors when searched seem to cause a system crash, though I did find some errors I was able to address despite not helping with this problem.

So, to explain additionally, I'm having some issues with graphic artefacts/misplaced or incorrectly rendered chunks (generally smaller than 150 px square) of the screen's images... for example, the smilies on the right of this entry field may also appear on a completely different part of the screen... and when the computer freezes the screen shudders and then this error happens on a huge scale with most of the screen affected.

This makes me think that there's a vRAM issue though it tested clean... so I was thinking it might be overheating, so I installed Temperature Monitor and got the following:



But I'm having trouble finding what acceptable temps are so, now that I've given all this info, I'm hoping one of you can help me out. I'm happy to answer any other questions you might have about the system and the problem.

If it is a temperature issue, I'd prefer to not hack my fan speed... is there a solution for helping the computer cool itself? I know it's a pain to get into the inner workings of the iMacs but would an internal dust clean-up help with this?

Hardware Overview:

Model Name: iMac
Model Identifier: iMac9,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.93 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 6 MB
Memory: 4 GB
Bus Speed: 1.07 GHz
Boot ROM Version: IM91.008D.B08
SMC Version (system): 1.37f3

I can only give you what I'm experiencing with a mid 2011 iMac.... All your temps with the exception of Ambient Air are high according to my readouts.

I don't know if your model iMac runs hotter or not, however, I kind of doubt it since every iMac I have experience with, runs fairly cool.

What I suggest is buy a triple pack of compressed canned air at your local computer store (Radio Shack, Office Depot, Staples, Best Buy, etc).

Remove all the cables and power from the iMac, and lay it face down on a soft cloth so that the bottom vents are exposed. Have a small vacuum handy.

Blow the compressed air through the vents at the bottom while at the same time run the small vacuum over the top vent. Hopefully that will blow what dust and dirt that's inside the machine around enough so that the vacuum will suck it out.

If that doesn't work, you may need to disassemble the machine to get at the insides. See the take apart instructions at iFixit: The free repair manual.

Of course if your machine is still under warranty or Apple care, ignore the above and make an appointment with your local Apple store and take it on in.

I have one version older Core 2 Duo iMac and I have installed the app to control the fans

Download smcFanControl for Mac - Control Intel Mac fans to make them run cooler. MacUpdate.com

Yes it works but it is slightly noisier as the fans are running at a higher RPM. I have set all three fan controls at 2500 rpm and it is cooler - I see 88 degrees for ODD. I run 2 external monitors and the video card was, and occasionally still does, give lines across the display. Lowering the temps has help to minimize the overheating and extended the life. Previously the temps were in the 125+ range and the screen would distort then freeze.

Thanks a lot for the input, both of you. Is it the consensus, then, that it is an overheating issue?

I'll try blowing out dust first and, if that doesn't work, I might take it in for a cleaning... I've seen the iFixit repair manuals for all of the various stuff and they're fun to look through but I'm uncomfortable doing it myself (particularly considering having to remove the entire pane of monitor glass) and would rather pay to have an Apple Authorized person do the repairs so that, if something goes horribly wrong, it's not my fault.

Unfortunately I'm not still under Apple Care as I bought the iMac in March of 2008, so, of course, just a short time out of warranty I'm up the creek.

Unfortunately I'm not still under Apple Care as I bought the iMac in March of 2008, so, of course, just a short time out of warranty I'm up the creek.

Click to expand...

Try blowing out the dust first - follow the procedure I outlined for you above - don't use anything stronger than canned air. If that doesn't work, take it on in to Apple but be sure to get an estimate before allowing them to perform the repairs.

yeah, smcfancontrol works great. I just got a iMac 24" and noticed that the default speeds were around 700rpm. When watching Netflix, it was getting pretty hot to touch on the top and still the fans were around the same. I upped the rpm to 2000rpm and it brought the temp somewhat lower but still pretty hot.

I run smc on my macbook pro all the time for the past 2+ yrs. When watching anything related to graphics, the MBP becomes very hot and cannot be placed on the lap anymore. The default speeds of the MBP are around 2000rpm and I up it to 5000rpm when it gets hot on the MBP.