The alternator does NOT have a clutch drive !! Unlike an electric motor, an alternator lacks permanent magnets and so no permanent magnetic field exists. This means that the pulley 'freewheels' whenever there is no field current going through the windings, such as when not charging. The presence of a field current creates a magnetic field, and it is this magnetic field which causes resistance to the pulley. This is overcome by the mechanical energy of the belt turning the pulley and generates the running/charging current in the process.
It is most likely the regulator, a series of 3 diodes. This is what regulates whether a field current is supplied to the windings or not. A replacement of the regulator will likely solve the issue.
But, there are concievably many miles on the bearings and so these too should be swapped if doing any maintenance to the unit at all.
Most cities in the US will have an auto electric shop which rebuilds alternators/starters. They can rewind the unit to produce more Amps, usually quite easily and the rebuild should come in under $100 in most cases. Shop locally and compare with off-the-shelf rebuilt units and go with the best deal.
Last edited by Lil bastard; 07-09-2008 at 10:14 AM.
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