One bad rectifier diode will cut an alternator's output to less than 1/3 of its rated capacity. It will still charge, and develop the right voltage, but two of the three phases cancel each other out so you're only charging the battery (or handling loads like headlights, heater fan, ignition, etc.) with one winding of the stator instead of all three, without enough current to meet the demand. For instance, a 55 amp alternator will drop to around 9-10 amps, maximum output. The battery has to make up the difference, and slowly discharges itself. The problem might not show up if the vehicle isn't run at night very often. One dead giveaway is a rattling noise and the alternator housing getting too hot to touch.
RUN- - - -do not walk away from a Powermaster- - - - -trying to put alternator windings in a housing that sort of resembles a generator is only good for show cars and others that spend most of their time on a trailer getting hauled to the next "show and shine".
Jerry
