Once you have chosen the right decoder and tested it, it’s time to check the installation instructions once more. Pay particular attention to the decoder wiring diagram provided.
Be sure you know the purpose of each wire and can identify where it should be soldered to the locomotive. In general decoders follow the NMRA DCC standard recommended wiring colors, but it’s always best to check just to be sure.
Note that several different types of light bulbs are used in locomotives and some lamp installations may require that you use current setting resistors to prevent the bulbs from burning out.
Be sure to follow the manufacturers’ instructions concerning light installations.