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Output Test

  1. Ensure connections at battery, alternator, and starter (most vehicles) are clean and tight. Ensure alternator, engine and body are properly grounded. Ensure alternator drive belt is tight and in good condition.
  2. Connect ammeter following manufacturer's instructions. Connect voltmeter leads to battery terminals. Adjust carbon pile on tester until voltmeter reads 13.5 volts. Alternator output should be 28-35 amps.
  3. Repeat process at 1000 RPM. Alternator output should be 75-85 amps. Repeat test at 2000 RPM. Alternator output should be 89 amps. If alternator output is low, remove alternator for testing and repairs.
  4. Start engine and run at 3000 RPM. Adjust carbon pile on tester to obtain maximum alternator output. DO NOT  allow voltage to go below 12.6 volts.
  5. Alternator output should equal alternator rated output, minus 16-20 amps. If reading is 16-20 amps below alternator rating, replace regulator and retest. If output is still low, repair or replace alternator.
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