Condensation behind iMac glass Screen, Moisture in an iMac:
iMac Screen Issue
According to the Apple support forum, more than a few users have experienced condensation behind the LCD. For now, there is no mention of any damage resulting from this, but as we all know, combining water and computers is never a good idea (unless you’re talking about water-cooled systems).
I have experienced condensation builds up in the lower corners and then comes back when the surrounding environment drops in temperature. This issue will re-occur each time the physical conditions are met. I did experience the Moisture in an Imac twice in just last one month.
First time I was told by Apple care to keep the iMac on till the time the unwanted condensation, moisture in an Imac vapor away. You need to go to system preferences, energy saver and change the setting of computer sleep, display sleep on never. Put it on that way .It took some 5 hrs for it to happen.
Second time it was bigger patch of condensation mark and the guy from apple service center came. He used Put off the protection glass with a sucker and did the cleaning by removing the screen glass. He did spray on LCD screen and glass and cleaned both before putting it back again. The video here is self explanatory.
Please see the video for explanation how Imac screen glass removal and cleanup.
So make sure to report the issue to Apple care if you’re seeing the same issues.
I was really surprised to hear the answer from the Apple care when I have logged a case and they have told me that their official standpoint is to leave the computer on for several hours and that the heat of the fans will drive the unwanted vapor away.
I think condensation should not happen in the first place, Especially with condensation and electronics! Hopefully Apple will step up and publicly recognize this as a fault sometime soon.