Chevrolet 70 1969 Series, Shop Manual

Page: 375 / 913

ENGINE ELECTRICAL 6Y-4
3. Check for loose cable connections, and for
evidence of corrosion. Correct as required before
proceeding with tests.
IN S T R U M E N T T EST
N O T E : A number of suppliers have approved
testing equipment available, such as the tester
(J-22552).
These testers have a programmed test pro­
cedure consisting of a series of timed discharge
and charge cycles, requiring approximately 2 to 3
minutes, that will determine the condition of the
battery with a high degree of accuracy. Whenusing
these testers, follow the procedures recommended
by the tester manufacturer. The battery should not
be charged prior to testing as doing so may alter
the test results.
The Following Test Should Be Used In
Conjunction With The Instrument Test:
1. Measure specific gravity of each cell, re­
gardless of state of charge.
2. If specific gravity readings show a differ­
ence between the highest and lowest cell of .050
(50 points) or more, the battery is defective and
should be replaced.
F U L L C H A R G E H Y D R O M E T E R T E ST
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 spec­
ific gravity is reduced. As temperature drops, the
electrolyte contracts and specific gravity increas­
es. Unless these variations are noted, the specific
gravity obtained by the hydrometer may not give
a true indication of the concentration of acid in the
electrolyte.
Corrections can be made for temperature by
adding .004 (four points of gravity) to the hydrom­
eter reading for every 10 F., that the electrolyte
is above 80° F., or by subtracting .004 for every
10°F., that electrolyte is below 80°F.
1. Adjust electrolyte to proper level in each
cell by adding water, then replace vent caps.
2. Charge the battery in accordance with ap­
plicable chart under "Charging Guide For Batter­
ies" earlier in this section.
3. Using a hydrometer, measure specific grav­
ity of electrolyte in each cell. If any cell reads
less than 1.230 (corrected to 80°F.) the battery
should be replaced.
C A U T IO N : DO NO T take hydrom eter
readings
im m ediately after water has been
added. Water m ust be thoroughly mixed
with
electrolyte by charging for at least
15 minutes at a rate high enough to cause
vigorous gassing.
4. If any cell reads above 1.310, the battery
may be returned to service. However, specific
gravities above 1.310 are harmful to the battery.
B A T T E R Y LIG H T L O A D T EST
N O T E : Do not attempt to perform this test on
vehicles equipped with batteries having a one-piece
cover (fig. 1).
Check electrical condition of battery cells as
follows (refer to fig. 2):
1. If electrolyte level in each cell is low, ad­
just to proper level by adding colorless, odorless,
drinking water.
2. Place load on battery by cranking engine.
If engine starts, turn off ignition immediately. If
engine does not start, hold starter switch " O N "
for 3 seconds, then release.
3. Turn on head lights (low beam). After one
minute, with lights still " O N ” read voltage of each
battery cell with voltmeter, compare readings with
the following:
Good Battery (Fig. 2, View A)
If all cells read 1.95 volts or, more and the
difference between the highest and lowest cell is
less than .05 volt, battery is good.
Good Battery (Fig. 2, View 6)
If cells read both above and below 1.95 volts
and the difference between the highest and lowest
cell is less than .05 volt, battery is good but re­
quires charging. See "Charging After The Light
Load Test" later in this section.
Replace Battery (Fig. 2, View C )
If any cell reads 1.95 volts or more and there
is a difference of .05 volts or more between the
highest and lowest cell, replace the battery.
Discharged Battery (Fig. 2, View D)
If all cells read less than 1.95 volts, battery
is too low to test properly. F A IL U R E O F T H E
M E T E R T O R E G IS T E R O N A L L C E L L S D O E S
N O T IN D IC A TE A D E F E C T I V E B A T T E R Y . Boost
charge battery and repeat "Light Load Test." (See
"Boost Charging For Light Load Test.") If battery
is found to be good alter boosting, it should be
fully recharged for good performance. If none of
the cells come up to 1.95 volts after the first boost
charge, the battery should be given a secondboost.
Batteries which do not respond after a secondboost
charge should be replaced.
N O T E : If any battery found to be good by the
"Light Load Test" does not perform satisfactorily
in subsequent service, it should again be tested by
the "Light Load Test" and if it still tests "good"
it should be removed from vehicle and tested as
outlined under " F U L L C H A R G E H Y D R O M E T E R
T E S T " previously on this page.
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U A L