Chosen Solution
Hello, Out of nowhere my mac shut down and when i tried to boot again, i got the infamous white screen after seeing the Apple Logo and loading bar. I tried the usual stuff Resetting NVRAM PRAM SMC. No effect. I tried to boot Verbose mode, at one point saw the screen glitch (colors mixed horizontally) and it tried to restart again (makes me think it is GPU problem) However, when i did Apple hardware Test it gave me following error Hardware Error 4MOT/4/40000003: HDD-1243 So i know that it is a Fan related error. Some people argued that if it was HDD-1244 error it was temperature sensor of the HDD. So my questions are Could you please let me know which error this is for? If it was some fan related issue would it prevent mac from booting ? What are the chances that it is because of GPU but for some reason Apple hardware test gives this error? GPU was replaced under warranty sometime around 2015-16 by Apple under replacement program. Also I removed the optical drive and put SSD instead a while ago. I am booting from the SSD not the default HDD that came with the imac.
4MOT is the fan, HDD is the given fan - No issue on what needs fixing! As to what you need to do is first open the system and in the process clean out the dust build up! I’m sure the fans are jammed with dust! Even still I would make the effort just to replace the HD fan iMac Intel 27" (Late 2009-Mid 2011) Hard Drive Fan As iFixit is out of stock and I think you’re in Europe give these folks a try TheBookYard UK - Mac 27" Fan - Hard Drive. It’s a bit of work as you need to remove the logic board to get to it. Be careful when lifting the sensor cables as there are two inductors which can be damaged if you’re not careful!
We don’t have a guide to pull the logic board fully out, but we do have a guide that will get you mostly there Installing iMac Intel 27" EMC 2429 Dual Drive Kit (HDD or SSD). Finish disconnecting the cables. As for the white screen… This sounds like your dedicated GPU has failed! As you need to pull the logic board to fix the fan take the time to take the GPU board off and clean off the old thermal paste (I would also do the CPU as well) Often times I find the thermal pads on the v-RAM on the board have degraded and also need replacement as well. Here’s a guide which will help explain how to pull the GPU board off iMac Intel 27" (Late 2009 or Mid 2010) Graphics Card Replacement Arctic Silver ArctiCleanArctic Silver Thermal Paste And here’s the needed thermal pads. Use a gap gage or a few strips of card stock to measure the distance between the RAM chips and the heat sink then select the correct size, you want a snug fit. Conductive Silicone Thermal Pad,100x100x0.5mmConductive Silicone Thermal Pad,100x100x1.0mmConductive Silicone Thermal Pad,100x100x1.5mm See if cleaning and repasting the GPU brings it back. Otherwise you may need a new GPU.
@lysander1 - Hi Emir, Did Dan’s proposal help you solve the problem? Having the same issue myself. I already took the machine apart and ordered a new HDD fan. But now I’m wondering if only the fan can cause wsod?
