Bench Tests

To remove the alternator, disconnect the battery ground cable and the leads at the alternator. Then unfasten and remove the alternator from the vehicle.

FIELD COIL DRAW
1. Place alternator on an insulated surface.
2. On all units, connect a jumper wire between one alternator field terminal and the negative terminal of a fully charged battery.
3. Connect test ammeter positive lead to the other alternator field terminal and the ammeter negative lead to the positive battery terminal.
4. On 1982---83 units except 100 and 114 amp, connect a jumper wire between alternator end shield and negative terminal of battery.
5. On all units, slowly rotate rotor by hand and note ammeter reading. On units except 100 and 114 amp, field current at 12 volts should be 4.5 to 6.5 amps (1984---88, 2.5---5.0 amps). On 100 and 114 amp units, field current should be 4.75 to 6.0 amps.
6. A low rotor coil draw is an indication of high resistance in the field coil circuit (brushes, slip rings or rotor coil). A high rotor coil draw indicates shorted rotor coil or grounded rotor. No reading indicates an open rotor or defective brushes.