On Car Test
Connect alternator as shown in Fig 1. Check that current through field winding (rotor) is 3.0 - 3.5 amperes. If current is not within specifications, check field winding condition and brush holder. Run engine speed to 1500 RPM. Alternator should then produce the specified current. Measure voltage at terminal "B+" and at terminal "61". Voltage should be 0.8 - 0.9 volts more at terminal "61". If not, isolation diodes are faulty and should be replaced.