Opel 1900 1973 Service Manual page 54

Figure lD-17 Checking Rotor for Ground
CHARGING
16. Check stator windings for a short, using a low
reading ohmmeter. Check two phases at a time by
holding ohmmeter prods alternately on winding
ends. Ohmmeter should read between .26 and .29
ohms. See Figure lD-20.
Figure 1 D-20 Checking Stator for Short
17. Clean slip rings with fine emery cloth and polish
them. To avoid generating flat surfaces on slip rings,
spin rotor on a lathe when cleaning and polishing.
Slip rings that are not concentric can be turned
a diameter of l-1/4 inches. When doing this,
to
remove only enough material to just clean up the
worn surface, then polish slip rings and blow clean
with compressed air.
18. If alternator current output is low one or more
of the nine diodes may be defective. See Figure lD-3.
19. If a defective diode is suspected, test diodes.
Before testing diodes, disconnect them, otherwise it
is not possible to determine which diode is defective.
Use a test light supplied with a DC voltage of not
more than 24 volts.
20. To test a diode, place one test light prod on diode
connection and other on diode housing, then reverse
test light prods. Test light should light brightly in
CONNECTION
(ANODE)
C U R R E N T ,
I
+ + HOUSING
(CATHODE)
HOUSING (AN&E) 3lMD2
Figure 1 D-2 1 Positive and Negative Diodes
SYSTEM
301 D20
down
CONNECTION
CURREN'
(CATHODE)
FLOW
I