When I plug headphones into output of MBP (15-inch Early 2008) with Mavericks – nothing changes, sound comes from internal speakers, nothing in System Preferences too. SMC reset, NVRAM cleared, sleep/wakeup – same situation:
UPDATE: Upgraded to 10.9.1 – no change
Best Answer
If you see red glowing light coming from it try the toothpick approach: take a toothpick and poke around in the jack until light turns off.
Source from: Apple inc
OS X Mavericks: Audio ports