Mercury 305 CID - Armature Tests; Field Coil Tests

4A-8 - STARTING SYSTEM 90-823225--1 1096
5. Check fit of bushing in commutator end frame. If
bushing is damaged or worn excessively, replace
end frame assembly. Apply SAE 20 oil to bushing
before reassembly. Avoid excessive lubrication.
6. Inspect armature commutator. If rough or
out-of-round, turn down and undercut. Inspect
points (where armature conductors join commu-
tator bars) for good, firm connection. Burned
commutator bar usually is evidence of poor con-
nection.
Armature Tests
TEST FOR SHORTS
Check armature for shorts by placing on growler and
holding hack saw blade over armature core while ro-
tating armature. If saw blade vibrates, armature is
shorted. After cleaning between commutator bars,
recheck. If saw blade still vibrates, replace armature.
01440
b
c
a
a - Hacksaw Blade
b - Armature Core
c - Growler
TEST FOR GROUND
1. With continuity meter, place one lead on arma-
ture core or shaft and other lead on commutator.
2. If meter hand moves, armature is grounded and
must be replaced.
01441
b
c
d
a
c
a - Commutator
b - Armature Core
c - Shaft
d - Growler
Field Coil Tests
TEST FOR OPEN CIRCUIT
1. With continuity meter, place one lead on each
end of field coils (insulated brush and field con-
nector bar).
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2. If meter does not move, field coils are open and
must be replaced.