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10-28
GENERATING SYSTEM
ELECTRICAL SYSTEMS
(304)
voltage is more than
%
volt greater than bat-
tery voltage, with 20 amperes flowing, it
indi-
cates that excessive resistance exists at some
point in generator to battery wiring. The cause
of high resistance must be located and elimi-
nated to insure proper charging of battery.
4. Slowly increase engine speed until am-
meter registers as follows, which should be
reached at approximately the speed shown
when generator is HOT, or at slightly lower
speed when cold:
Model Year
Amperes
Engine RPM
1948
34 to 36
1400
1949
40
1250
CAUTION: Do not exceed engine speeds indi-
cated when F terminal is grounded.
5.
If
the specified amperage cannot be ob-
tained at approximately the speed indicated,
the generator does not have proper output.
It
should be removed for a bench test (par. 10-
27) and the necessary corrections should be
made before making any adjustments on the
generator regulator.
10-27 BENCH TEST OF GENERATOR
The following inspection and test of genera-
tor, after removal from car, may be used to
determine the cause of unsatisfactory output
before generator is
disassembled.
1. Remove cover band and inspect condi-
tion of brushes and commutator as described in
paragraph 10-26
.
If
brushes and commutator
are in satisfactory condition and the cause of
trouble is not apparent proceed to the following
steps.
2. Place piece of cardboard between com-
mutator and grounded
brush.
Using test lamp
and points, check for grounds with test points
on "A" terminal and generator frame.
If
lamp
lights, the generator
is'
internally grounded.
Locate the ground by insulating the other brush
also, and checking the brush holders, armature,
commutator and field separately.
3. If generator is not grounded, check the
field for open circuits by placing one test lamp
point on the "F" terminal and the other point
on the brush holder to which the field is con-
nected. If lamp does not light the field has open
circuit. If the open circuit is due to a broken
lead or bad connections, it can be repaired but
if the open circuit is inside one of the field coils
the coil must be replaced.
4. If the field is not open, check for a short
circuit by connecting a 6-volt battery and an
ammeter in series with the field
coils.
Proceed
with care since a shorted field may draw exces-
sive current which might damage the ammeter.
On 1.948 models, an ammeter reading of 1.75
to 1.9 amperes indicates field is satisfactory; a
higher reading indicates a
short
circuit. On
1949 Series 50-70, the ammeter reading should
be 1.90 to 2.03
amperes.
5.
If
a grounded or
shorted
field is found
check the generator regulator contact points
since either condition may have permitted an
excessive field current which will have burned
the contact points. Burned contact points re-
quire removal of regulator for cleaning or re-
placement of points
(par.
10-30).
6.
If
the
cause
of trouble has not been lo-
cated it will be necessary to disassemble gen-
erator for test of armature, as described in the
following paragraph.
10-28 GENERATOR REPAIRS-ON
BENCH
The generator brushes may be replaced with-
out disassembling the generator, but all other
internal repairs require disassembly.
If
commutator has burned bars or is worn
eccentric, new brushes will wear out very
quickly if commutator is not trued up at time
brushes are installed.
a. Replacement of Generator Brushes
When inspecting or replacing generator
brushes, do not pull them out of their holders
against spring tension by pulling on the brush
leads. This may loosen the leads in the brushes,
causing excessive resistance, heating, and open
circuits to develop. Do not snap brush arms
down on brushes as this may clip or crack them.
Make sure that brushes are free in the hold-
ers and that springs have proper tension. Ex-
cssive tension will cause rapid brush and com-
mutator wear, and low tension will cause arcing
and burning of brushes and commutator. Hook
a spring scale on end of brush arm and measure
pull required to just lift arm off brush, pulling
at right angle to brush
arm.
Tension should
be 24 to 28
ounces,
and may
be
adjusted by
bending the brush spring as
required.
New brushes must be seated to make good
contact with armature, using a brush seating
stone. This is a soft abrasive material which,
when held against a revolving commutator, dis-
integrates so that particles are carried under
the brushes and wear their contracting faces
-1
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