Yanmar 4JH2E Service Manual page 342

Chapter 9 Electrical System
4. Alternator
3) Rotor coil insulation test
Check the continuity between the slip ring and the
rotor core, or the shaft. If there is continuity, insulation
inside the rotor is defective, causing a short with the
earth circuit. Replace the rotor coil.
4) Check the rear side ball bearing. If the rotation of the
bearing is heavy, or produces abnormal sounds,
replace the ball bearing.
(3) Stator
1) Stator coil continuity test
Check the continuity between each terminal of the
stator coil.
If
there is no continuity, there is a wire
break in the stator coil. Replace the stator coil.
Resistance value
Printed in Japan
AOA1029-9002
Approx. 0.077Q at 20°C
1 ·phase resistance
2) Stator coil insulation test
Check the continuity between the terminals and the
stator core. If there is continuity, insulation of the
stator coil is defective. This will cause a short-circuit
with the earth core. Replace the stator coil.
(4) Brush
The brush is hard and wears slowly, but when it is worn
beyond the allowable limit, replace it. When replacing
the brush, also check the strength of the brush spring.
To check, push the spring down to 2mm (0.0787in.)
from the end surface of the brush holder, and read the
gauge.
Brush spring strength 255-3459 (0.56
~
0.761b.)
(5) Brush wear
Check the brush length.
The brush wears very little, but replace the brush if worn
over the wear limit line printed on the brush.
Wear limit line (brush)
mm(in.)
Maintenance standard Wear limit
Brush length 16 (0.6299)
9 (0.3543)