10-04-2018 03:27 AM
You're the first user to have experienced the exact same issue.
I've purchased the OWC Thermal sensor and installation kit.
I'm just working up the courage to remove the screen again and install it.
I'll let you know how I get on.
Many thanks for the post, much appreciated.
10-08-2018 11:49 AM
I've removed the replacement screen and installed the OWC Thermal Sensor.
I then tested the performance (before committing the screen) of the iMac and the problem is still occurring.
So I tried a new SATA drive with a clean OS and the problem is there also.
It appears there is another temperature sensor that is built into the LCD screen, and this may not be present on the replacement LCD.
I'll investigate further.
10-08-2018 06:30 PM
@sckennedy If you still have your Apple original hard drive, you could reinstall it along with your new LCD Panel to make sure the issue is with the LCD Panel and not the OWC thermal adapter. If your original drive was failing, I think you could still do an Option Boot to check if the fans run at high speed, or you could boot your new SSD externally. You might want to try running the Apple Hardware Test as it might tell you which sensor is having issues. If the iMac did not come with a DVD with the Hardware Test, then you can possibly initiate it by booting the iMac by holding down Option-D. You could also reconnect your damaged LCD panel just to confirm the original setup or the OWC thermal adapter is working.
Also double check all of the cable connections on the Logic Board to make sure something wasn't accidentally dislodged or damaged.
You may want to check the iFixIt website to see if they mention any sensors on the LCD panel. I've never worked on this model so I cannot say where the sensors are located.
10-09-2018 09:04 AM
This might seem like an odd suggestion, but people should try installing High Sierra by formatting the drive as default Extended Journaled format type instead of APFS. There is no reason you need to format a drive in APFS when installing High Sierra, since it will make the appropriate transition during the OS deployment. In fact the instructions I can find online all say to format Extended Journaled when doing a recovery reinstall.
It wouldn't surprise me (especially with some older Macs) if letting the OS install making the conversion to APFS is necessary for everything to run smooth. Otherwise this could make no difference whatsoever, but worth a shot I say.
10-18-2018 12:59 PM
Sorry my last comment must not have been clear. Thereis defintely a small sensor on the back of the LCD its a 4" long very thin wire with a stamp sized sendor attached. Good luck