Portable electronic appliances typically come with 12-volt adaptors and patch cords that enable such appliances to be used inside vehicles. In the United States, production of 12-volt automobile plugs is standardised under "UL standard 2089," which covers plugs and patch cords that insert into cigarette lighter receptacles. A 12-volt car lighter adaptor plug is easy and convenient to use, but can sometimes become defective due to abuse or misuse. If you know how to rewire a defective car lighter adaptor plug you can save yourself some cash.
Cut the cord attached to the lighter plug about 2 inches below the plug, using diagonal pliers. Remove about 2 inches of outer covering from the tip of the patch cord, using diagonal pliers. Strip off 1/2 inch of insulation from the tip of the two inner wires (positive and negative), using a wire stripper.
Look at the plug. Observe the two retractable metal fins protruding on each side of its cylinder, and the retractable metal nipple at its tip. Note that the side fins are negative conductors, and that the tip is the positive conductor of the 12-volt circuit.
Hold the plug cap in your right hand, hold the cylindrical body in your left hand, and twist the cap counterclockwise to unscrew the cap from the plug's cylindrical body. Find the holding screw along the adaptor plug's cylindrical body, and unscrew it with a screwdriver. A lighter plug is typically split lengthwise along its centre into two identical halves. Open the cylindrical body to reveal the metal fins and nipple inside, including a small spring that pushes the retractable metal nipple.
Note the order in which the metal conductors and spring are arranged inside the plug's cylindrical body. Remove the existing wires attached to the metal nipple, and to the metal fins, by cutting the wires using diagonal pliers.
Loop the stripped end of the positive wire (red, or black with white stripe) around the base of the metal nipple (positive terminal), and solder the copper wire to the metal nipple, using a soldering gun and solder wire.
Wrap the stripped end of the negative wire (black, without stripe) around the base of the metal fins. Fasten the wire onto the fins, using soldering gun and solder wire. Replace the metal nipple and metal fins inside the plug, and reassemble the plug in the same arrangement as you had found them earlier. Make sure that the positive and negative wires do not come in contact with each other.
Turn on your vehicle's ignition switch. Insert the car lighter adaptor plug into a 12-volt receptacle on your vehicle's dashboard, and turn on your appliance to test the connection.