How do you replace voltage regulator on 2003 Honda Shadow?

The voltage regulator is also known as a rectifier in shop talk and is easily replaced. The recifier is held in place with two machine screws. Simply loosen and remove the screws, then disconnect the black plastic connector that connects the rectifier to the wiring harness. There is a black protective cover around the connector which needs to be pulled back a bit in order to unplug the connector. In case you have rectifier problems, such as overheating or the wires to and from it getting fried, resulting in a dead battery and starting problems, then you should check out if there is a short to earth somewhere or any wire connectors gone bad. Also check if there is a short in the stator wiring. Rectifer problems are common on older bikes because the wiring harness and the connectors get worn or shorted. Some people have simply done away with the connectors and soldered the wires together. This is especially true of some of the connectors found below the seat. I know of at least one case where such soldering of wires and elimination of connectors fixed a recurring rectifier problem.