External mic not working / disable?

[whiteboxamir]

If I don't have my apple earphones plugged in, the internal mic works fine. When I plug them in, however, it switches to external mic and the mic isn't working. Anyway to disable external mic and just use the earphones for output only? It's either a hardware issue with the macbook air (2012, lion), or the earphones mic is not working.

I also still have the hardware issue with the camera and will be fixing/replacing the mac in a few days.