Sound randomly switches from headphones to speakers

I'm having the same problem.

Any ideas?

I've been having this problem for as long as I've had my Macbook Pro, but it only happens sporadically. But when it does, it keeps on bugging me for at least an hour.

I don't know if a restart will help, but I think (as described by another reply) it's related to the sensor that determines what type of connector is used in the jack input.

[offtopic but interesting]Is this forum even remotely interesting to Apple staff? Every topic I've started or replied to did not solve my problem. It seems Apple people don't have answers to these kinds of problems or are just cannot be bothered to answer them.[offtopic]

it sounds to me like you (all of you) are having some sort of a problem with the microswitch inside the headphone jack that switches between different modes (headphone, speaker, and fiber-optic (the red light)).

Apart from plugging in headphones and un-plugging them a few times, there isn't really a lot you can do without taking it into a repair shop and getting it fixed properly.

Having this exact same issue as well. Just wanted to let you know you're not alone. So ANNOYING!

Ditto here on sound on and off, with a slight variation from those described above -- and, possibly, a major pre-existing condition in development.

First, the possibly overarching issue: A few days ago, after air travel and all that entails, I was not able to boot up in the usual manner in an airport along the way. Once arrived at my destination I again kept getting the dread, small question mark midscreen beside a tiny version of the blue and white head profiles connected with the Mac logo. So I rebooted holding down Apple-C. After the screen scrolled through a few black and white screens of technical data in true PC nerd form, the machine did initiate the usual start-up screens. I logged in and was able to manipulate all programs. On the following day, I had the same problem turning on the machine. I have not dared turn it off since then.

New Issue: Intermittent Sound. I opened Safari and iTunes today. The audio cuts out after a few seconds, but I can regain it by tapping into the internet streaming with the headphone jack. Then the audio through the headphones cuts off. When I pull out the headphone jack, I hear the speakers normally again. Then they go silent and I switch back to the headphones. This also happens when I am not on the internet but merely playing music files in my iTunes library. If I leave the machine to go to another room for a while, I sometimes hear the sound coming back randomly for short periods. All audio preferences have been checked out, and the First Aid utility verifies that the HD is OK. (The current HD was replaced six months ago, when I also got an external HD for backups.)

After the move to a new geographical area I am, of course, in the hands of a different cable provider -- in case that means anything. A second Mac, an iBook, which also made the trip, is working just fine beside this old machine. So is the motherboard (5 yrs old) beginning to die? Or is there a software fix?

Yes, I am currently backing up files to the external hard drive.

Many thanks, if you can offer a diagnosis. --JJ

I've had similar problems with my hard drive. After swapping it for a 500GB WD-drive, everything seemed fine. But then, I got really weird effects where applications would just freeze, but I was able to use Expose to switch to other apps. One by one they froze, until there was nothing else to do but to hard reset the Mac.
After doing that, I would get the Folder icon with the question mark, indicating that the operating system could not be found/mounted. This is most likely a Hard Drive issue, but when I connected it to an HP desktop computer and ran a comprehensive surface scan using the WD diagnostic tool, it reported no errors. Disk Utility did not report any error either.
After some debate I remembered the one thing I did before everything came apart, and that was installing The Missing Sync. When I uninstalled that app, everything seems fine. So it may even be a due to a faulty written program that you installed recently and forgot about. Otherwise it might be wise to start a new topic for that particular problem.

About the sound problem: I found out that it does not matter much if you have the headphones plugged in or not. When playing sound over the speakers, the same behavior may be noticed (i.e.: the Mac will think that headphones are plugged in, even if they're not). I'm going to send an e-mail to my local Apple Care center, because this ***** monkeyballs.