Mitsubishi S4S Service Manual page 149

2.2 Inspeetion
(1) Brushes
Replace the brushes if they are wom down to the
service limit line.
Unit: mm [in.]
18.5mm[
[0.73 in.]
ELECTRICAL SYSTEM
Service limit
____=r
Item
Assembly Service
Standard Limit
Brush
112 V -50A
18.5 [0.73] 7 [0.28]
length 24 V -25A 18.5 [0.73] 5 [0.20]
(2) Field coil
Measure the resistance between the slip rings. If
the resistance is out of assembly standard, replace
the rotor.
Item Assembly Standard
Resistance 12 V -50A 2.40
in slip rings
[20°C [68°F] 24 V -25A 12.4 0
(3) Stator coil
Check for continuity between the lead wires. If
no continuity is noted, the coil is open-circuited.
Also check for continuity between the lead wire
and coil. If a continuity is noted, the coil is
grounded.
(4) Rectifier
Test the resistance between each diode lead wire
and heat sink. To test, conneet the positive (+)
lead wire of the tester to the diode and then the
negative (-) lead wire of the tester to the diode.
If the resistance is infinite in both cases, the diode
is open-circuited, If it is nearly zero in both cases,
the diode is short-circuited. If the diode is open-
or short-circuited, replace the rectifier.
5 mm [0.20 in.] [24 V]
7 mm [0.28 in.] [12 V]
Checking brush
Testing field coil
Testing stator coil
Trio diodes
Testing rectifier
12-11