Ultimate Ears headphones are similar to most other types of earbuds in the sense they're not particularly durable and won't normally last more than a year or two. Most of the time headphones like these stop working, their wiring has loosened or detatched. If you know the correct steps, you can save the cost of replacing your headphones and instead repair the wiring yourself. You'll need a soldering iron and a few simple tools.
Cut off the jack with scissors, exposing the wires. The jack is the connector that that plugs the headphones into your device. Throw the old jack away.
Strip back one-half to one inch of the outer cord casing, exposing the one red, one green and two copper-coloured wires at the end of your headphone cord. To strip the casing, gently place the headphone cord between your thumb and the knife's sharp edge and pull the cord in a twisting motion. The knife will cut the casing, which you then slide off the end of the wires.
Identify and separate the wires. Twist the two copper wires together to create one.
Heat the ends of all wires, very briefly, using a lighter or match. This burns off any remaining insulation and is vital for making the headphones work.
Unscrew the new 3.5mm jack casing by hand. You should see three small, circular and tube-shaped terminals that jut out slightly at the thick end of the tip. This is where you will solder the wires.
Heat up the soldering iron. While you're waiting, place the thin end of the new jack inside the vice and clamp it together tightly.
Wipe the soldering iron tip against a damp sponge to clean it. Melt a small amount of solder onto the soldering iron by gently pressing the soldering iron tip against the silver solder.
Solder all three wires to the correct terminal by pressing the tip of the soldering iron against the wire and the terminal, making sure it's touching both. The copper wire goes into the largest terminal, the green wire goes into the central slot and the red wire is soldered to the remaining terminal.
Screw the jack back together. If everything is correct, your Ultimate Ears should be working again. If they still do not work, try applying more solder. If you attached the wires the wrong way, remove the joints by heating solder wick onto them and then repositioning and reattaching the wires in a different sequence. If the headphones still fail, your remaining option, unfortunately, is to buy new ones.
Purchase a stereo, not mono, jack plug. They look similar, but only a stereo plug will work for the Ultimate Ears. Be careful not to burn yourself when using the soldering iron. Ensure that you use a vice or equivalent to secure the jack, as holding the metal end will burn you quickly. Do not hold the sponge in your hand when using it to clean the solder, as this can also burn. Solder kits come with a stand for the sponge.