Headphones only work if already plugged in when the Mac is turned on

Naramis

Registered
I have a 13” mid-2012 MacBook Air running Mountain Lion.

I recently noticed this problem with headphones. If I plug them in when the laptop is already running, they don’t work at all. Sound continues to play through the speakers, and the OS doesn’t recognize that headphones were plugged in.
If I go to Sound on the System Preferences, the headphones don’t show up at all on the list of output devices; only the integrated speakers show up.
If I alt-click on the sound icon on the top bar, there are no headphones listed under output devices either. The sound continues to play normally through the speakers as if the headphones weren’t plugged in.

However, if I plug in the headphones when the machine is turned off, and then turn it on, they work perfectly (well, sound quality isn’t great, but they work).
If I then unplug the headphones and plug them back in, they don’t work anymore as described above.

I tested this with multiple headphones, all of which work normally on other devices like my PC, iPod and Android phone. I tried resetting PRAM and that other thing (SNC?), didn’t work either.

I don’t think it’s a hardware problem, since it works normally under specific conditions. Sounds more like a software bug, but I’m no expert..

I searched around for issues like this, but only found generic answers which didn’t solve the problem, as well as unanswered posts.
 
Do you still have issues with plugging in headphones, when you are logged in to a different user account?
Make a new user just for this purpose.
 
Did you mean to answer "Nope", as Nope implies that you don't have issues when logged in as another user, and your answer is therefore ambiguous (at least, to me :D )

Assuming that you meant that your audio problem continues - Go into the main Library folder, then Preferences.
Delete all files that have the word "audio", such as com.apple.audio.SystemSettings.plist

The audio files might even be in their own "Audio" folder in Preferences.
Just drag that folder to the trash. You might be asked for your admin password, so enter that, if needed.
That folder would be system wide, so restart your Mac, then try out your headphones again.

If no help, download and install the 10.8.4 combined updater, and try the headphones again.

If the combined updater does not change anything, then boot to your recovery partition, and reinstall OS X.

And, if it still fails, take your Macbook Air in for service.
 
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If the change of user accounts doesn't help it might be some dust, etc. in the port, if a re-install doesn't help.

Get a toothpick and gently (barley in and turn it around and around to clean stuff out). Make sure you go into the port to far. See if that helps.
 
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