Diode Trio Test

Remove diode trio from end frame. Connect an ohmmeter probe to brush terminal and other probe to one of the stator winding terminals. Check resistance on lowest range scale. Note reading and reverse leads. If readings are the same, replace diode trio. Check other 2 stator terminals of diode trio in same manner. Connect probes between any 2 stator terminals, if resistance is zero, diode is shorted and must be replaced.