Which fuse runs the alternator?

Almost every alternator has its output directly connected to the battery or connected by a "fuse link" (which is a high-current fuse that looks like a section of the wire from the alternator to the battery). The alternator is isolated by internal diodes so as not to drain the battery when the engine is off. The alternator is turned on by power which comes in thru the "ALT" warning light. When the engine is started, the alternator has no output, so current flows thru the bulb and into the alternator field (F) winding. When the winding spins it generates voltage which then feeds back to the light and the internal regulator to power the alternator. When the alternator is self-powered, there is power on both sides of the "ALT" light, so it is NOT illuminated. When the alternator stops producing power, the bulb lights up. Note that the "fuse" is whatever fuse is connected to the "ALT" light. If the "ALT" light bulb or the fuse which feeds the start-up power to the light is burned out then the alternator will not power-up. Newer cars with digital dash instruments use a resistor in place of the "ALT" light bulb.