My headphone jack sometimes not responding to headphones.

"I have exactly this problem and here is what seems to fix it:

1. Bring up system preferences - and 'sound' settings within it.

2. connect your headphones or jack lead into the audio socket.

3. From the apple icon menu in the top left corner of the os x screen, tell your computer to go to sleep

4. Immediately wake it up again from sleep

5. A second or two after waking, under 'output'; 'internal speakers' should change to 'headphone port'.

NB. Weirdly, this fix switches the output to headphone port, but you lose the option for internal speakers at the same time. However, to switch back to internal speakers, remove the headphone/jack lead, put the computer to sleep then re-wake it. This switches it back.

Hope this helps! Peace ;)"

"This works (it is a Lion bug):

Under Sys Pref> Sound > Click on Internal speakers. Then at the bottom set audio port for ""sound output."""

"Hi, I have an early 2011 MacBookPro and it has the very same problem.

This solution solved my problem:

Start music or video or anything that produce sound on internal speakers (my internal speakers are muted, it’s no matter)Plug in your earphone while the music/video still playing"

"@night4cat, exact same problem here - Headphones not detected when plugged in after sleep, same thing when the port is used for line-out or with another headphones set. This is almost certainly a firmware issue since the machine never fails to recognize the headphones after a reboot. It is not physical port damage.

For now the best workaround is to use a USB DAC such as the USB adapter supplied with Beyerdynamic MMX2 headphones, or just reboot. For a real fix I think we will be waiting on Apple for a software update.

Update

Hey night4cat: if you don't know how to measure impedance I strongly recommend you don't do it. Firstly, it's pointless - this is nothing to do with hardware. Secondly, you have a warranty and you should be taking your machine to an Apple authorized service centre if you still don't believe me, not tinkering with it yourself. If you do mess with it, and you create a hardware problem by incorrectly applying meter probes or by some other method, then you will have a hardware problem and you won't have a warranty any more either.

Why is it definitely not a hardware (bad socket or headphone) problem?

1. Reliably occurs after system sleep.

2. Fixed by reboot.

3. Mac headphone jack is also software controlled, it is not a simple analog output controlled by a mechanical switch alone! How do we know this? Look at System Preferences - you can have something plugged into the headphone jack and still direct audio output elsewhere, such as a USB DAC.

Try this also - Play some music through internal speakers. Insert headphone jack while wearing just one earpiece. You will notice that the music does not immediately start coming through the headphones. The switch inside the headphone jack causes the system to mute the output, switch to the jack and then unmute. Same in reverse when you pull the plug, the system mutes, switches to internal speakers and then unumtes. You can even slow this down by running all your cores flat out (encoding video for instance) - this is software controlled, it is not an ancient transistor radio with a simple mechanical switch. There is a switch to detect whether something is plugged in or not but all it does is supply an input to the system, not connect/disconnect the internal amplifier output.

If you have a real hardware problem, like a crackly headphone jack - and you're out of warranty. And you can handle disassembling your machine, replacing a part and then reassembling it, then I'm all for buying parts from iFixit and doing it yourself.

But not when it isn't a hardware problem, and not when this non-existent problem would be Apple's responsibility to fix under warranty (or software update) anyway."