> Why is the starter motor not effected by the change from positive
> ground to
> negative ground.
For the same reason the heater fan, and the wiper motor are not affected.
They all use windings for both the armature and field. So, for one polarity
you have a magnetic north pole attracting a magnetic south pole (and vice
versa on the opposite side of the armature/field); then for the other
polarity you have a magnetic south pole attracting a magnetic north (and
vice versa on the opposite side). The polarity of the poles changes, but
the effect is exactly the same.
The durn things will actually run on AC (although I don't recommend you try
this), the design is what's known as a 'universal' motor because of this
ability to run on either DC or AC.
The only reason you have to polarize the generator is because it relies on
'residual' magnetism in the housing and pole pieces to get started in the
absence of field current. Once there is field current flowing, it happily
generate either + or -, depending on the polarity of the field current.
Randall
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