Rectifier Short or Grounded and Stator Grounded Test

Fig. 20 Testing Diode Trio:

Fig. 21 Alternator W/integral Regulator Rectifier Short Or Grounded And Stator Grounded Test:

Using a suitable ohmmeter, connect one probe to alternator BAT (B+) terminal, Figs. 20 and 21, and the other probe to the STA terminal (rear blade terminal). Then, reverse the ohmmeter probes and repeat the test. A reading of about 6.5 ohms should be obtained in one direction and no needle movement with the probes reversed. A reading in both directions indicates a bad positive diode, a grounded positive diode plate or a grounded BAT terminal.
Perform the same test using the STA and GND (ground) terminals of the alternator. A reading in both directions indicates either a bad negative diode, a grounded stator winding, a grounded stator terminal, a grounded positive diode plate, or a grounded BAT terminal.
Infinite readings (no needle movement) in all four probe positions in the proceeding tests indicates an open STA terminal lead connection inside the alternator.