The diode is usually necessary to prevent current feedback to the ignition system if you're not using an idiot light. The engine will run on if enough current feeds back from the alternator to keep the coil firing. The #2 wire can be connected directly to the big battery terminal at the back of the alternator housing, but the #1 wire needs to have switched voltage either from the coil input or the ignition switch. A 100 ohm 10 watt resistor works about as well as a diode.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!