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Output Test

NOTE: Ensure "B+" connection (heavy Gray wire) at alternator is tight and insulating sleeve is not pinched between nut and washer. Alternator output may be reduced if connection is loose.
  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. Start engine and run at 3000 RPM. Adjust carbon pile on tester to obtain maximum alternator output. Do not allow voltage to drop below 12.6 volts.
  3. 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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