2012 Mountain Lion Macbook Pro screen brightness control disappear

A late reply, but maybe it can help someone else. I was having the same problem (brightness keys not working, brightness slider not shown in the Displays - System Preferences) with the same model 2012 MacBook Pro, running 10.11.6 El Capitan. I then found that the keys and preferences worked if I changed to another user (an Admin or a Guest user), and also the keys worked on the login screen. After I restarted the Macbook Pro, the problem cleared up. I was glad I didn't try some of the other suggestions seen in other similar questions like resetting the PRAM or some Terminal commands.

So my basic suggestion is to try with another user account or the login screen, which can rule out keyboard hardware problems.

JohnnyChin95,

if you open up the Keyboard pane of System Preferences, and select the Keyboard tab, is the “Use all F1, F2, etc. keys as standard function keys” checkbox checked, or is it unchecked?

If you try each of your function keys in turn, either F1, F2, &c. or Fn+F1, Fn+F2, &c. depending upon the state of the checkbox above, which function keys work properly, and which don’t work properly? For example, does Mission Control appear when F3 (or Fn+F3) is pressed? Does the Dashboard appear when F4 (or Fn+F4) is pressed? and so on.

JohnnyChin95,

have you tried resetting your MacBook Pro’s System Management Controller yet, to see if that makes a difference with its F1 and F2 keys’ functionality?

Do you have reason to believe that your MacBook Pro is a counterfeit? (As you can see from these discussions, problems occur even on genuine Apple products.)

JohnnyChin95,

I don’t know which forms of support Apple offers in Malaysia, but in the US they only offer support by telephone — no support by e-mail. I haven’t downloaded Mountain Lion myself, but the Mavericks download was over 5 GB; my guess is that Mountain Lion would not be bigger than Mavericks. I don’t understand what you mean when you ask if your Mac is original — since I misunderstood the opposite of original as being “counterfeit”, what do you mean by a non-original Mac?

JohnnyChin95,

reïnstalling OS X will probably be the only real solution. Will your house have Internet before your warranty expires? If not, then it would probably be better to send it to Apple, even though there would be a long wait to get it back; you’ve paid for the warranty in your purchase price, so why not make use of it? (You might also want to consider purchasing an AppleCare plan; you can do so any time before your original warranty expires.) Alternatively, do you know anyone with Internet access who would be willing to let you download OS X onto your MacBook Pro at their home?

To my knowledge, all of the original MacBook Pros are manufactured in China; I don’t know where in China, though. If you received a box that has a sticker with your MacBook Pro’s serial number, Ethernet MAC address, Wi-Fi MAC address, &c., and all of that information matches what’s in your MacBook Pro, then that’s probably a good sign that you have an original Apple product.

In my case, I have a relatively slow 3½ Mb/s downstream DSL connection, so it took about five hours for me to download Mavericks. If your Internet speed will be faster, then your download time should be proportionally shorter.

JohnnyChin95,

I’ve never run Mountain Lion on my MacBook Pro, so I don’t know if installing the 10.8.5 upgrade would fix your function key problem in 10.8.3 or not. If you fear that there could be a hidden problem, then your best option would be to make use of your warranty and send your MacBook Pro to Apple for them to make things right (and update to 10.8.5 when you get it back, if they haven’t done it for you).