Headphone audio not working.

[UDidWhat]

My built in speakers work fine all the time, even when i have headphones plugged in. I looked under the output devices in the system settings and the only option is for built in audio output, a.k.a speakers, there is no option for an alternate audio output, a.k.a headphones. When i plug in my headphones nothing happens, sound continues out of the internal speakers like nothing happened. How do i fix this ( at home for free)?

I have Mac OS X version 10.4.11.. iMac7,1.. 2 Ghz Intel Core 2 Duo 1b 667 mgz DDR2 SDRAM

 

[hughvane]

It seems that the headphone jack is not opening the little audio switch (cancelling internal speakers) inside the Mac (what model, what OS?). That is unusual, but it could indicate a broken or otherwise malfunctioning contact inside the audio-out port. How to fix it? Not easy, depending on the model of Mac, because it means opening up the machine.