Cadillac 60 Series 1963 Shop Manual page 286

ELECTRICAL SYSTEM
12-5
2. Light Load Test
1. Check battery level. Add water if necessary.
2. Remove high tension lead at distributor cap
and ground lead.
3. Place a load on the battery by holding the
ignition switch in the start position, cranking the
engine for three seconds.
NOTE: This step must be done to condition
the battery for testing, even though the battery
is so low it won't crank the engine. If the engine
starts, the ignition must be turned off immedi-
ately; otherwise, the surface charge will not be
removed.
4. Operate headlights on low beam for at least
one minute.
5. After one minute, and with headlights still
on, read the individual cell voltages of the battery
with a voltmeter having .01 volt divisions. Start
with the cell next to the positive terminal and go
around the battery in a clockwise direction as
shown in Fig. 12-4. Carefully record each cell
reading, then compare readings with the follow-
ing to determine the condition of the battery.
UNIFORM READINGS-If any cell reads 1.95
volts or more, and the difference between the high-
est and lowest cell is less than.05volt, the battery
is good. If any cell reads less than 1.95 volts, the
battery should be charged for maximum perform-
ance.
NON-UNIFORM READINGS-If any cell reads
1.95 volts or more, and there is a difference of
.05 volt or more between the highest and lowest
cell, the battery should be replaced.
NOTE: When cell capacities cause the cell
voltage readings to differ by .05 volt or more,
the battery has a defect that will cause short
life or poor performance.
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LOW READINGS-If all cells read less than 1.95
volts, the battery is too low to test properly and
must have a booster charge.
NOTE: Most defective batteries will fail the
light load test. However, there are a few bat-
teries that will pass this test, but still fail to
perform satisfactorily in service. These bat-
teries should again be tested using the light load
test; if test results are still good, the battery
should be removed from the car and given the
Full Charge Hydrometer Test as explained in
Note 4.
3. Use of Hydrometer
The hydrometer measures the percentages of
sulphuric acid in the battery electrolyte in terms
of specific gravity. As a battery drops from a
charged to a discharged condition, the acid leaves
the solution and enters the plates, causing a de-
crease in specific gravity of electrolyte. An indi-
cation of the concentration of the electrolyte is
obtained with a hvdrometer.
The specific gravity of the electrolyte varies
not only with the percentage of acid in the liquid
but also with temperature. As temperature in-
creases, the electrolyte expands so that the spe-
cific gravity is reduced. As temperature drops,
the electrolyte contracts so that the specific
gravity increases. Unless these variations in
specific gravity are taken into account, the spe-
cific gravity obtained by the hydrometer may not
give a true indication of the concentration of acid
in the electrolyte.
Fig. 12-3 Fuse Panel
Fig. 12-4 Checking Cell Voltage