John Deere stx38 - Manual (Page 162)

4 - 78
3/21/97
REPAIR ELECTRICAL
4. Clean stud terminal (F), replace if threads are
stripped or if it is corroded.
5. Replace insulator (E) if cracked.
6. Clean positive brushes (D )contact point with end
cap. Using Ohmmeter, check for no continuity
between positive brushes (D) and end cap, and
also between stud terminal (F) and end cap.
Replace positive brushes (D) if continuity is
indicated.
7. Align upper highlighted markings (A) and carefully
assemble top end cap and armature into frame.
8. Compress brushes into brush holders of bottom
end cap using two thin screw drivers (G) or tongue
depressors.
9. Align lower highlighted markings (A) and carefully
assemble starter so brushes are positioned
against commutator of armature.
10. Carefully remove screwdrivers without allowing
brushes to dislodge from holders of bottom end
cap as assembly goes together.
11. Install long cap screws (B) and tighten them evenly.
12. Install starter in reverse order of removal.
REPAIR STARTER ARMATURE
IMPORTANT: DO NOT clean armature with solvent.
It can damage insulation on windings. Use
mineral spirits and a clean brush.
1. Clean commutator of armature with a coarse, lint
free cloth. DO NOT use emery cloth. If
commutator is badly grooved, turn it down on a
lathe or replace it.
2. Check for short circuits with a growler.
3. Rotate armature on growler while holding a steel
strip (e.g. hacksaw blade) on armature. Strip will
vibrate in area of short.
NOTE: Shorts between bars are sometimes caused by
dirt or copper between bars.
If test indicates short circuited windings, clean
and recheck. If still faulty, replace armature.
4. Check for grounded windings with an ohmmeter or
test light. If any continuity is indicated, winding is
grounded and armature must be replaced.
NOTE: Armature windings are connected in parallel,
each bar must be tested.
5. Check for open windings with an ohmmeter or test
light. If no continuity is indicated, there is an open
circuit and armature must be replaced.
M55917
F
D
E
M55919
G
M46892
M55923
M55924