Breaks cause no current to flow. Fuses blow for excessive current, as in a wire rubbed through the insulation and grounding out to something metal. Components can also be shorted internally. That's rarely caused by the ignition switch.
A simple trick is to replace the blown fuse with a pair of spade terminals, then use a pair of small jumper wires to connect them to a 12 volt light bulb. When the short is present and the circuit is powered up, the bulb will be full brightness, so don't lay it on carpeting or against a plastic door panel. Now you can unplug things and move wire harnesses around to see what makes the short go away. When it does, the bulb will go out or get dim. The bulb's resistance will limit current flow to a safe value.
Saturday, September 3rd, 2011 AT 4:56 PM