Kohler K91 Owner's Manual page 165

B.
Testing for Short in Alternator System
Disconnect charging lead from battery, and connect charge
lead test lamp in Series between battery and charge lead.
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 dire leading back to the
battery is shorted. If light goes out, diode is defective.
(See section for testing diode).
C. Testing Diode
Disconnect charge lead plug from charge lead. Using
multimeter set on resistance scale, 'check diode by attach-
ing one meter lead to red stator. lead wire (a needle may
be used to pierce stator lead wire insulation). Touch the
other multimeter lead to diode pin in plastic connector,
then reverse meter leads. The meter should show continuity
in one direction only. If meter shows a reading in both
directions or does not show continuity in either direction,
the diode is defective and must be replaced.
D. Testing Stator Charging Coils
Remove blower housing, flywheel etc. and examine red lead
wire for cuts, damaged insulation
or
obvious short on
leads; if bare spots cannot be repaired replace stator.
Stator should also be checked for continuity as follows:
Use multimeter set on resistance 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.
Next remove screw which attaches stator ground wires to
stator laminations, Be certain ground wire does not touch
laminations 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.
Note: Discoloration of stator coils does not mean stator
is defective. A shorted diode will pass battery current
through stator coils to ground, which discolors coils due
to heat. Replacing diode would normally restore alternator
without replacing stator.
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