New 27" iMac Brightness Control Missing

Question

New 27" iMac Brightness Control Missing

I have a brand new 27" iMac. Currently the only things plugged into it are the Apple-branded wireless keyboard and mouse that were included with the iMac and ethernet. I waited for the 10.9.2 update to see if that would resolve the issue, but it has not. I have also performed multiple PRAM and NVRAM resets.

The F1 and F2 keys on the Apple-branded keyboard do not decrease or increase the brightness of the internal display. In System preferences -> Display, there is no brightness slider at all. It is behaving as if I plugged in a generic 3rd party display.

I am about to copy over the

AppleBackligt.kext

AppleBacklightExpert.kext

AppleUSBDisplays.kext

from an identical 27" iMac (that doesn't have this issue) to see if that will resolve the issue.

Unfortunately, a complete reinstall of Mavericks is not an option at this time.

Thank you in advance for all your help and suggestions.

Edit: fixed title typo

Posted on Feb 27, 2014 6:45 AM

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Answer 1

Feb 27, 2014 6:58 AM in response to Andy Pichotta

It is possible your keyboard needs the fn key to help out.

Go into your System Preferences > Keyboard and see if you have the option "Use all F1, F2, etc. keys as standard function keys" checked. If so, then you need to hold down the "fn" key while choosing the brightness keys (F1 and F2).

Uncheck it if you want it the other way around.

Hope this helps.

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Answer 2

Feb 27, 2014 7:14 AM in response to Timothy Fink

I've already tried this. I'm not as concerned about the function keys working, I think that will fix itself once I'm able to get the brightness slider to reappear in System Preferences -> Displays. However, I have not been able to get it to appear. The check box for auto-brightness does not exist there either.

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Answer 3

Feb 27, 2014 7:34 AM in response to Andy Pichotta

Have you found any display preferences to see if trashing those brings back the slider?

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Answer 4

rkaufmann87

Level 10

148,452 points

Feb 27, 2014 7:38 AM in response to Andy Pichotta

Andy,

You have 90 days of free AppleCare telephone support, that should be the first thing you do is pick up the phone and give them a ring. If the first engineer isn't able to assist ask for the case to be escalated. If you don't know the number for AppleCare in your corner of the world please click http://support.apple.com/kb/HE57 to get started.

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Answer 5

Feb 27, 2014 7:48 AM in response to rkaufmann87

I've already got the issue traveling through the AppleCare channels. Their quick fix has been a complete reinstall, which again I am tryign to avoid at this time. I am an enterprise customer.

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Answer 6

Feb 27, 2014 7:56 AM in response to Andy Pichotta

Does that mean you don't have the time to reinistall, or it will be a major IT pain?

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Answer 7

Feb 27, 2014 8:05 AM in response to Timothy Fink

It is currently unavaible for reinstall, due to the time (albeit short) required. If I can't fix this another way, that's the route I'd like to take. I'm just hoping I can find a more direct solution, and to find out if this issue is just this machine or broader.

The steps I plan on taking right now are,

Verify the display is properly set up by Apple (maybe the internal USB isn't plugged in right?)

Replace .kext files listed above from an identical iMac with working brightness.

Dump any preferences related to the display I can find.

Reset NV/PRAM again.

Reinstall the OS.

Replace.

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Answer 8

PomalinK

Level 1

0 points

Mar 22, 2015 3:36 PM in response to Andy Pichotta

I am having same issue with my Late-2012 iMac 27". Did you find a fix for this? I even tried reinstalling OS X 10.10.2

Still no brightness slider bar. The functions keys doesnt work. The screen is stuck on full brightness!!!

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Answer 9

poikkeus1

Level 4

2,474 points

Mar 22, 2015 5:18 PM in response to PomalinK

It's possible that the problem is hardware related, but some have had success with Terminal. Another post (for a MacBook) yields a possible solution:

http://askubuntu.com/questions/244853/brightness-controls-dont-work-on-macbook-s tuck-on-high-nvidia-geforce-9400m

Post if this, or if your other suggestions worked.

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Answer 10

PomalinK

Level 1

0 points

Mar 22, 2015 6:02 PM in response to poikkeus1

The brightness control actually works on Windows 8.1 bootcamp. So i'm not sure its hardware related. I even tried the 3rd party software such as Shades & Brightness. But those 2 software only adds tint to the picture while the actual backlight stays brights.

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Answer 11

jandrc

Level 1

0 points

Sep 9, 2015 6:35 PM in response to PomalinK

Has anyone found a solution to this yet? I have the same problem: no ability to control brightness from the keyboard, no brightness slider controls in Display Preferences. Some folks apparently found that zapping the PRAM helped, but not in my case. I've been talking to AppleCare for over two weeks on this and still no solution.

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