i know this is too late to be of any benefit to you now but in case someone else faces this again.
1. get a cheap multimeter - the $4 versions will work just fine.
2. set the resistance to the lowest setting.
3. measure the resistance between the lower ring of the plug and either the tip ( left channel ) or the middle ring ( right channel ) - assuming TRS plug with 3 contacts , if TRRS ( 4 rings - one for mic ) bottom ring and top 2.
hope you got it fixed.
..dB