ALTERNATOR
Dual Circuit - Rectifier Plug Type
TESTING FOR SHORT IN ALTERNATOR SYSTEM
Disconnect charging lead from battery, and connect
charge lead test lamp in series between battery and
charge lead. (Figure 169) DO NOT START ENGINE.
Test lamp should not light. If it does light, stator charging
lead is shorted or diode is defective. Disconnect charge
lead connector at alternator. If test light does not go out,
the lead from the cap to the battery is shorted. If light
goes out, diode is defective.
Fig. 169 - Testing for Short in Stator,
Diode or Charge Lead
TESTING DIODE
Disconnect connector plug. Set meter on ohm scale.
Check diode by attaching one meter lead to red stator
lead wire. (A needle may be used to pierce stator lead
wire insulation.) Touch the other meter lead to diode join
in plastic connector, then reverse meter leads. The
meter should show a reading in one direction only. If
meter shows a reading in both directions or does not
show a reading in either direction, the diode is defective
and the connector assembly must be replaced. See Fig.
170.
Fig. 170 - Testing Diode
NOTE: Service replacement diodes are pre-assembled
to a connector and a short lead wire for ease of
installation.
TESTING STATOR CHARGING COILS
Remove blower housing, flywheel etc. and examine red
lead wire for cuts, damaged insulation or obvious short
on lead. If bare spots are found repair with electrical
tape. If short cannot be repaired, replace stator. Stator
should also be checked for continuity as follows:
Use VOA meter set on ohm scale. Touch one meter
lead to stator laminations, touch the other meter lead to
red stator charge lead wire. (Pierce red wire insulation
with a needle to insure meter lead contact.) Meter should
show continuity. Fig. 171.
Next remove screw which attaches stator ground wires
to stator laminations. Be certain ground wire does not
touch laminations as shown in Fig. 171 and repeat
previous test. Meter should not show continuity. If meter
does not show continuity in first test or shows continuity
during second test, stator is defective and must be
replaced.
Fig. 171 - Testing Stator
NOTE: Discoloration of stator coils does not mean stator
is defective. A shorted diode will pass battery current
thru stator coils to ground, which discolors coils due to
heat. Replacing diode would normally restore alternator
without replacing stator.
53
