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Alternator Output Test

  1. To bench check alternator proceed as follows: Make connections as shown in illustration, except leave carbon pile disconnected. Use a fully charged battery, and a 10 Ohm resistor rated at 6 watts or more between alternator No. 1 terminal and battery. Slowly increase alternator speed and observe voltage. If voltage is uncontrolled with speed and increases above 16 volts, check for a grounded brush lead clip. If brush lead clip is OK, replace regulator.
  2. Connect carbon pile. Operate alternator at moderate speed and adjust carbon pile to obtain maximum output. If output is within 10% of rated output as stamped on alternator frame, alternator is good. If not, ground alternator field with a screwdriver. If output can be adjusted to within 10% of rated output with field grounded, replace regulator. If output is not within specifications, check field winding, diode trio, rectifier bridge and stator.
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