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Battery Overcharge

  1. Turn all electric loads off. Disconnect negative battery cable. Disconnect wire at alternator "B" terminal. Connect a 60-amp or larger ammeter between the wire and terminal "B". Reconnect the negative battery cable. Charge the battery until the charging rate is less than 5 amps or replace with a fully charged battery. Reconnect negative battery cable, start engine and operate at 2500 RPM. If less than 5 amps are present, go to next step. If 5 amps or greater is present, go to step 4).
  2. Turn ignition switch to "OFF" position. Disconnect negative battery cable. Disconnect "B", "L" and "R" or "S" connectors from alternator. Using an ohmmeter, measure resistance between alternator "L" and "E" or "F" terminals. If resistance is 2-4 ohms, go to next step. If not, rotate pulley and check resistance again. If resistance is unchanged, there is a problem in rotor coil or brush.
  3. Reconnect the "B", "L" and "R" or "S" connectors to the alternator. Reconnect negative battery terminal and turn ignition switch to the "ON" position. Using a voltmeter, check voltage between alternator "L" terminal and ground. If voltage present is 1-3 volts, alternator is okay. If voltage is over 3 volts, IC regulator or rotor coil is faulty.
  4. With system prepared for testing as in step 1), measure voltage at terminal "L" at an engine speed of 2500+ RPM. If voltage is 14.1-14.7, alternator is okay. If voltage is greater than 14.7, there is an internal alternator fault.
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