Field Open Or Short Circuit Test
- Set ohmmeter in "x1" range. Touch regulator terminal "A" with one probe. Touch terminal "F" of regulator with other probe and spin alternator pulley. See Fig 1. Reverse ohmmeter connections and repeat test.
- In one test, ohmmeter should read between 2.2-100 ohms resistance and may fluctuate while pulley is spinning. In reverse connection, ohmmeter should fluctuate between 2.2-9 ohms.
- An infinite reading in one test and about 9 ohms resistance in reverse test indicates open brush lead, worn or stuck brushes, bad rotor assembly or loose mounting screws at regulator brush holder.
- Resistance reading of less than 2.2 ohms in both tests indicates shorted rotor or bad regulator. Reading considerably greater than 9 ohms in both tests indicates a defective regulator or loose terminal "F" screw.
- Connect ohmmeter probe to alternator rear housing. Connect other probe to terminal "F" screw. See Figure. Reverse probes and repeat test. Ohmmeter should read infinity in one direction and approximately 9 ohms in other direction. Reading less than infinity in both directions indicates grounded brush lead or bad regulator. Reading greater than 9 ohms resistance in both directions indicates bad regulator or damaged terminal connection.
Courtesy of FORD MOTOR CO.