21 ½ iMac screen suddenly goes dim

[pm-r]

Rod, both times it has happened the bar graph for the brightness has been hard over to the left.

I wonder if the same problem could be related to this and their fix:

Second, after shutting down the system for an hour or so, it came back on fine for about 15-20 minutes, then the screen started doing its dimming again. Got me thinking it might be a thermal problem somewhere. Well, a little more searching on the internet turned up some cases where the display did funny things when the system got hot ... and there were specific references to checking the ventilation holes on the bottom of the iMac as well as the vent strip on the top. Lo and behold, there was an awful lot of dust clogging over half of the vent holes on my iMac! So I vacuumed everything out, clean as a whistle.
...
Who would have thought dust in the vents would have caused this? I'm glad it seems to have been that simple a fix.

It seems the dust in the vents was causing the iMac to overheat which in-tern lowered the brightness of the display...

Or maybe just a thorough dusting internally might be needed...

iMac screen dims by itself (not set to au… - Apple Community

discussions.apple.com

Maybe worth having a look inside???




- Patrick
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[Jonzjob]

Dust? DUST?? I'll let you tell SWMBO that she hasn't dusted properly

Seriously, for once, I had a look at top and bottom. Top seemed OK, but there was a bit of dust in its bottom, but now vacced out. So I now wait with baited breath.

Who would have though that it was even possible? But then again after 18 years of fixing hardware on the big stuff it should have come to mind. It always surprised me that in so called 'clean rooms' there could be so much dust and dirt.

Once again folks, thank you!

 

[pm-r]

Dust? DUST?? I'll let you tell SWMBO that she hasn't dusted properly

I wouldn't be the first person to say that dusting can actually just lead to moving it around so it can land and new different places. And God only knows how much dust is covering the internal circuit board circuits and stuff.

How dusty was it in France where you lived for a number of years??? Maybe some of it got inside as well.

Anyway, let's hope the vacuuming of the cooling vents helps, and just maybe could have been the cause.

Do you have or use an internal temperature sensing utility like Macs Fan Control.app??? It might be a good idea to use it and keep an eye on it and the iMac's internal temperatures.

Info and download:

Macs Fan Control - Help & Support

crystalidea.com

- Patrick
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