What is wrong with my MP3 player when the volume changes every time I touch the wire?
By “touch the wire” I presume you mean the chord connecting the headphones to the player. This problem could be caused by an intermittent fault anywhere in the headphone, e.g., where the wire(s) enters the earpiece(s), in the wire, and at the jack. Wiggling the wire may make the fault come and go. It is also possible that the jack in the MP3 player is dirty or bent and no longer working properly. You can check if the problem lies in the headphone by using a different pair of headphones on the player. If the problem goes away, there is a fault in the wire, most likely where it is bent back and forth routinely, e.g., at the jack or where it enters the headphones. If you know someone with repair skills, they might be able to fix it by replacing the wire and jack. If the problem does not go away, the problem lies in the headphone socket in the MP3 player itself. The socket can be cleaned by (very carefully) using a cleaning swap wet with tape head cleaner or any other alcohol-based cleaner
