left side not working

sunil gupta, it is either the plug or the connection on the driver (speaker). To test it use a multimeter and place it on ohm reading. Touch the contact, either tip or ring, with one probe and the other probe on the driver. If you have continuity it is the driver if you do not, then it is the plug. Of course, check to make sure the wires are connected on your driver. Use this guide to get to the driver. Here is a guide that shows how to replace the plug. Different headphones, same principle. Hope this helps, good luck.