GMC S Series 1994, Repair Manual

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6. Low no-load speed and low current draw indicates
a higher internal resistance due to poor connec­
tio n s, d e fe ctive leads, d irty com m utator, and
causes listed under step 5.
7. High free speed and high current draw indicates
shorted fields. If shorted fields are suspected,
replace the field coil assem bly and check for
improved performance.
DISASSEMBLY
IN TR O D U C TIO N
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
replacem ent of parts. The 28-M T com ponents are
shown in figure 3.
Do not attempt to disassemble the following compo­
nents that are serviced as assemblies:
• Solenoid assembly (19)
• Clutch drive assembly (34)
• Brush holder assembly (7)
• Armature assembly (13)
• Frame and field assembly (15)
As a precaution, it is suggested that safety glasses
be worn when disassembling or assembling the starter
motor.
U N IT DISASSEMBLY
❖
Disassemble (Figure 4)
• Clean the outside of the starter housing, removing
grease, oil, mud, etc.
• Scribe marks completely down one side of the
starter motor to ensure proper alignment of all
components during assembly. Use a colored pencil
or marker that will show on all parts.
1. Motor lead on the frame assembly (A) from the
solenoid assembly (19).
• Remove the nut from the motor terminal, slip off
the motor lead, and reinstall the nut.
2. Two through bolts (1).
3. Two brush plate screws (2).
4. Commutator end frame (3) and O-ring seal (4).
Important
• In the following step, take care not to lose the
small dowel pin (16) installed between the
frame assembly (A) and the gear reduction and
drive group (B). The dowel pin is needed for
assembly and must be saved. If it is lost, it
m ust be re p la ce d w ith a 2-m m x 10-mm
(0.079-inch x 0.394-inch) long pin obtained or
manufactured locally.
5. Frame, field, and brush holder group (A), dowel pin
(16), and O-ring seal (17).
• The armature assembly (13) may come off with
the frame, field, and brush holder group (A) or
may be retained by the gear reduction and
drive group (B).
6. Armature assembly (13) with bearings (12 and 14).
• Do not remove the bearings from the armature
assembly unless replacement is required. Refer
to “ Cleaning, Inspection, and Repair.”
7. Solenoid screws (18).
8. Solenoid assembly (19).
• Pivot the inside end of the solenoid assembly
(19) out of engagement with the shift lever in
the gear reduction and drive group (B) to with­
draw it.
FRAME, FIELD, AND BRUSH
HOLDER GROUP
❖
Disassemble (Figure 5)
1. Insulated brush screws (9).
• M ove the brush holder a ssem bly (7) with
brushes slightly away from the frame and field
assembly (15) to reach across with a screwdriv­
er and remove the screws (9).
2. Frame and field assembly (15).
3. Grounded brush screws (6).
4. Brushes (5 and 8) if they need replacement.
• Grasp the brush end of each brush spring (11)
with needle nose pliers. Twist the spring end
away from the brush socket on the brush holder
assembly (7) and remove the spring.
5. Brush springs (11) if they need replacement.
All electrical components should be inspected and
tested. Refer to “ Cleaning, Inspection, and Repair.”
GEAR REDUCTION AND DRIVE
GROUP
❖
Disassemble (Figure 6)
1. Housing bolts (25 and 26).
2. Armature support bracket (27).
Important
• Washers (28 and 30) may stick to the bracket
or to the drive shaft and clutch group (C) as the
bracket is removed. In either case, note the
position and number of each of these washers.
3. Washers (28 and 30).
• Save the washers to be installed in the same
position and number at assembly.
4. Drive housing plug (21) and plate (24).
• Pry out the drive housing plug with a large
screwdriver.
5. Shift lever nut (23), washer (22), and screw (38).