The starter solenoid has a switch inside it that provides voltage to the
motor. The key switch only provides voltage to the solenoid section. The
solenoid then actuates and closes a switch that supplies voltage to spin
the motor. The solenoid is built onto the starter as a unit but it can
be replaced separately once the complete starter is removed. Few people
do this as it is easier to just get a whole rebuilt starter unit.

DISCONNECT the battery before doing anything with the starter as it has
a direct connection even when the key is off. That is why it can do what
yours is doing.

Mark

John McLean wrote:
>..................
> My question is :
> Does the power to the starter motor come entirely through the ignition
> switch thereby indicating my switch is bad?
> Or, is there a source of power to the starter motor independant of the
> ignition switch which may indicate an
> intermittent sticking contact.   (note that the solenoid was not engaged
> during this phenomenon)
>
> Thanks,
>           John McLean   87   Vanagon  GL