Chosen Solution
Hello from germany! My iMac 24" from early 2009 hangs up all the time but without an indicated pattern… What happened when? Sometimes (1-2x/day) the iMac hangs up when i work with my iMac, sometimes he hangs up when the device is in idle (the mac is on but i do nothing on it). The iMac is becoming very hot on the upper left back. When the failure happens, it seams that the display its repeating to send the last picture (it hangs) an the mac isn’t reacting on commands from keyboard or mouse. When i listen to music, then this sound hangs up also. The fans are running all the time. Then the only option is to press the power-button 5 seconds an shut the mac down. After the manually restart the system appears to work fine. I have try to wait when the failure occur - but after seven hours the results are the same: nothing reacts. Hardware-background: Processor: 2,93 GHz Intel Core 2 Duo, Graphic: NVIDIA GeForce GT 120 256 MB8 GB Corsair 1067Mhz DDR3 Ram (2x4 GB)640 GB HDD Software-background: at the moment i have installed OS X 10.8.2 - in the past OS X 10.5.8 and 10.6.8 on the same machine - the symptoms are the same. So i think there is no reason for an software-failure. The Programs i used every day are: Firefox, Creative Suite CS5 (Photoshop, Indesign, etc.), Aperture, iWork, iLife. But because the system also hangs up when “no” program is open and the system is in idle i wouldn’t look for a reason in this programs. Things i have done in the past to locate the failure: i change the ram-modules -> not the reason, the failure occur againi made a software update from OSX 10.5 to 10.6 -> not the reason, the failure occur again i formatted the hdd an reinstalled the system OSX 10.5 an upgrade it to 10.6/10.8 -> not the reason, the failure occur againi repair permissions with the disk tool from apple -> not the reason, the failure occur againde-/activate the airport / plug/unplug the lan-cable -> not the reason, the failure occur againbring the iMac to an GravisStore - in the tests from this company no failure occur What can be the reason? Is there an bug on the motherboard/graphic? can the power supply be a reason? What can i do?
Addition: two pictures about the temperatures measured with istat.
Bevor do anything:
After switch to “medium” fan control
Your iMac has a thermo cut off circuit so when it gets to hot it will shut down. You can try using some compressed air to blow out the vent areas hopefully dislodging the dust build up that could be causing your system to over heat. More likely one of the fans is not working. You can try running an application to monitor your temperature and fan sensors to see which area is suspect Temperature Gauge. Depending on your skill set you could try replacing the defective fan or bring your system into an Apple Store and have them fix it. Sorry to say there isn’t a fan replacement guide. Here’s the guide to pull the display unit so you can access the fans iMac EMC 2267 Its also possible you just have a lot to dust build up inside as well.
