iPod only plays through one earphone.

Hi.

I have a 5th gen iPod video 30gb.

I've had it for years, but recently it has started to only play music through the left earphone.

I've checked that the earphones work and that my songs are stereo instead of mono.

The most interesting thing is that when I plug it into my car's head unit by the dock connector at the bottom, it still only plays music through the left speakers of my car, so it can't just be an issue with the headphone jack, surely?

I imagine that there could possibly be an incorrectly set fader setting somewhere, but I can't seem to find where that would be.

If anybody has any ideas on how to resolve this issue, I'd be much obliged.

Thanks.