Chevrolet 30 Series 1967 Service Manual page 354

ENGINE-ELECTRICAL 6Y-6
H O LD
D O N O T S U C K
TUBE
IN T O O M U C H
V ERTICAL
ELECTROLYTE
FLO AT M UST
BE FREE
Fig . 7b—Testing S p e c ific G r a v ity
4. Hold hydrometer vertically and draw in just enough
liquid from battery cell so that float is free floating.
Hold hydrometer at eye level so that float is vertical
and free of outer tube, then take reading at surface
of liquid. Disregard the curvature where the liquid
rises against float stem due to surface tension.
5. Avoid dropping battery fluid on car or clothing as
it is extremely corrosive.
should be washed off immediately with baking soda
solution.
The specific gravity of the electrolyte varies not only
with the percentage of acid in the liquid but also with
temperature. As temperature increases, the electrolyte
expands so that the specific 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 specific
gravity obtained by the hydrometer may not give a true
indication of the concentration of acid in the electrolyte.
A fully charged Battery will have a specific gravity
reading of approximately 1.270 at an electrolyte tem­
perature of 80°F. If the electrolyte temperature is
above or below 80°F., additions or subtractions must
be made in order to obtain a hydrometer reading cor­
rected to the 80°F. standard. For every 10° above 80°F.,
add four specific gravity points (.004) to the hydrometer
reading. Example: A hydrometer reading of 1.260 at
110°F. would be 1.272 corrected to 80°F., indicating a
fully charged Battery. For every 10° below 80°F., sub­
tract four points (.004) from the reading. Example:
A hydrometer reading of 1.272 at 0°F. would be 1.240
corrected to 80°F., indicating a partially charged Battery.
SPECIFIC GRAVITY CELL COMPARISON TEST
This test may be used when a instrument tester is
not available. To perform this test measure the specific
gravity of each cell., regardless of state of charge, and
interpret the results as follows:
TAKE R E A D IN G
AT EYE LEVEL
Any fluid that drops
Fig. 8b—Battery In stallation C - K A 10-20, CA-30
• If specific gravity readings show a difference bet­
ween the highest and lowest cell of .050 (50 points)
or more, the Battery is defective and should be
replaced.
INSTALLING BATTERIES (Fig. 8b)
Battery installation varies depending on the truck
model and series. To install a Battery properly, it is
important to observe the following precautions:
• Connect grounded terminal of Battery last to avoid
short circuits which may damage the electrical
system.
• Be sure there are not foreign objects in the carrier,
so that the new Battery will rest properly in the
bottom of the carrier.
• Tighten the hold-down evenly until snug (60-80 in.
lbs.). Do not draw down tight enough to distort or
crack the case or cover.
• Be sure the cables are in good condition and the
terminal clamps are clean and tight. Make sure the
ground cable is clean and tight at engine block or
frame.
• Check polarity to be sure the Battery is not re ­
versed with respect to the generating system.
CHEVROLET TRUCK SERVICE M ANUAL