GMC C Series 1993, Руководство по ремонту

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6D4-4 37-M T STARTER MOTORS
• If the armature does rotate freely, the motor
should be given a no-load test before disas­
sembly.
THERMOSTAT CHECK
(OVERCRANK PROTECTION)
1. Be sure the motor is cool, when the circuit should
be closed.
2. Connect an ohmmeter to the two thermostat termi­
nals on the motor (figure 2).
3. The ohmmeter should read zero (continuity). If not,
the thermostat has an open circuit. Replace the
thermostat and lead terminal assembly.
NO LOAD TEST
Connect a voltmeter from the motor terminal to the
motor frame (figure 7). On starter motors with ground
terminals, connect to that rather than the frame. Use an
rpm indicator to measure pinion speed.
Connect the motor and an ammeter in series with a
fully charged battery of the specified voltage, and a
switch in the open position from the solenoid battery
terminal to the solenoid switch terminal. Close the
switch and compare the rpm, current, and voltage read­
ings with the specifications at the end of this section. It
is not necessary to obtain the exact voltage specified. A
good reading can be made by understanding that if the
voltage is slightly higher, the rpm will be slightly higher,
with the current remaining basically unchanged. Howev­
er, if the exact voltage is desired, a carbon pile con­
nected across the battery can be used to reduce the
voltage to the specified value. Compare the test results
to the specifications at the end of this section.
Figure 7— No Load Test Hookup
Make disconnections only with the switch open. Test
results may be interpreted as follows:
1. Rated current draw and no-load speed indicate
normal condition of the starter motor.
2. Low free speed and high current draw indicates:
° Too
much friction.
Tight, dirty, or worn bear­
ings, bent armature shaft or loose pole shoes
allowing the armature to drag.
• Shorted armature. This can be further checked
on a growler after disassembly.
•
Grounded armature of fields.
Check further
after disassembly.
3. Failure to operate with high current draw indicates:
• A
direct ground,
in the terminal or fields.
• Seized bearings. This should have been noted
by turning the armature by hand.
4. Failure to operate with no current draw indicates:
• Open field circuit. This can be checked after
disassembly by inspecting internal connections
and tracing the circuit with a test lamp.
•
Open armature coils.
Inspect the commutator
for badly burned bars after disassembly.
•
Broken brush springs, worn brushes.
High
insulation between the commutator bars or oth­
er causes which would prevent good contact
between the brushes and commutator.
5. Low no-load speed and low current draw indicate a
higher internal resistance due to poor connections,
defective leads, dirty commutator, and causes list­
ed under step 4.
6. High free speed and high current draw indicate
shorted fields. If shorted fields are suspected,
replace the field coil assembly and check for
improved performance.
DISASSEMBLY
If the motor does not perform to specifications, it may
need to be disassembled for further testing of the com­
ponents. Normally, the starter motor should be disas­
sembled only so far as is necessary to make repair or
replacement of the defective parts. As a precaution, it is
suggested that safety glasses be worn when disassem­
bling or assembling the starter motor.
FIELD FRAME
|«"»| Remove or Disconnect (Figures 8 through 12)
A. Clean the outside of the starter housing, removing
grease, oil, mud, etc.
B. Scribe marks to show the relationship of the drive
housing, lever housing, field frame, and end frame
to aid in assembly.
1. Field coil terminal to solenoid connector (58) and
two Screws.
2. Nut (64) if present, nut (2), washers (3, 4), and
terminal insulator (5) from the end frame. The
square insulator is located inside the end frame.
3. Thermostat retaining ring (65) from the thermostat
(12) on starters with overcrank protection.
4. Four end frame screws (6).
5. End frame (9) from the field frame.
• Hold the end of each brush spring off the end of
each brush while pulling the brush out of the guide