LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Oldsmobile >> 1990 >> Custom Cruiser >> Repair and Diagnosis >> Electrical >> Charging Systems >> Alternator & Regulator >> Bench Testing >> Alternator Output
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Alternator Output

CAUTION: Carbon pile testing is part of this procedure. To avoid explosion, turn carbon pile OFF before connecting it to or disconnecting it from vehicle battery.
  1. Mount alternator on test stand. Be sure ground polarity of alternator and battery are the same. Ensure battery is fully charged. Connect voltmeter, ammeter, carbon pile (in OFF position) and 30-500 ohm resistor between the battery and the terminal "L" of alternator. See Fig 1 .
    Fig 1: Alternator Bench Test
    G90J04583Courtesy of GENERAL MOTORS CORP.
  2. Rotate alternator by hand in clockwise direction. Slowly increase alternator speed and observe voltage. If voltage is uncontrolled and increases to more than 16 volts, rotor field is shorted and/or regulator is defective. A shorted rotor field coil can cause regulator to become defective.
  3. If voltage is less than 16 volts, increase speed and adjust carbon pile to obtain maximum amperage output. Maintain voltage at 13 volts. If output is within 15 amps of rated output, alternator is okay. If output is not within 15 amps of rated output, repair or replace alternator. See ALTERNATOR SPECIFICATIONS  at the end of this article.
scientia non olet · About LEMON Manuals