Leather,

The reason solonoids use pick and hold coils is so heavy guage wires are not needed to go to the solonoid and a heavy current terminals are not needed in the key switch. Since the pick coil is energized for only a split second, the lighter guage wires and contacts do not overheat. The hold coil doesn't overheat either. Also there is more current available to the starter to crank the engine.

The pick current goes thru the starter until the solonoid contacts are closed. Then the voltage at the pick coil goes from 0 to +12 volts (because it is connected to the + terminal on the starter) and thus there in no longer any current going thru the pick coil windings I.E. it has 12 volts at each end of the windings. The hold coil which draws much less current has current flowing thru it as long as the key switch is held in the start position.

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