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Alternator Output Test

CAUTION: Carbon pile testing is part of this procedure. To avoid battery explosion, turn carbon pile OFF before connecting to or disconnecting from test stand battery.
NOTE: Bench test can be used to verify operation of CS144 alternator after repairs.
  1. Mount alternator on test stand. Set test stand controls to turn alternator clockwise. Ensure ground polarity of alternator and battery are the same. Ensure battery is fully charged. Connect voltmeter, ammeter and carbon pile (in the OFF position). Connect a 30-500 ohm resistor between battery and terminal "L" of alternator. See Fig 1 .
    Fig 1: Bench Testing Alternator
    G90J04583Courtesy of GENERAL MOTORS CORP.
  2. Slowly increase alternator speed while observing voltmeter. If output is uncontrolled and increases to greater than 16 volts, rotor field coil is shorted and/or regulator is defective. A shorted rotor field coil can cause regulator failure.
  3. If voltage is less than 16 volts, increase speed and adjust carbon pile to obtain maximum output current. Maintain voltage greater than 13 volts. If output is within 15 amps of rated output, alternator is okay. If output is not within 15 amps of rated output, replace alternator. See ALTERNATOR USAGE/AMP OUTPUT RATING  table.
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