On a maintenance-free sealed battery, a built-in hydrometer or "eye'' is used for checking the fluid level and specific gravity readings. If your battery is equipped with an eye, use it for checking the condition of the battery by observing the color of the eye. A green colored eye indicates good condition and a dark colored eye indicates the need for service. Replacement batteries could be either the sealed (maintenance-free) or non-sealed type.
FLUID LEVEL (EXCEPT MAINTENANCE-FREE SEALED BATTERIES)
See Figure 1
Check the battery electrolyte level at least once a month, or more often in hot weather or during periods of extended operation. The level can be checked through the case on translucent polypropylene batteries; the cell caps must be removed on other models. The electrolyte level in each cell should be kept filled to the bottom of the split ring inside, or to the line marked on the outside of the case.
If the level is low, add only distilled water, or colorless, odorless drinking water, through the opening until the level is correct. Each cell is completely separate from the others, so each must be checked and filled individually.
If water is added in freezing weather, the truck should be driven several miles to allow the water to mix with the electrolyte. Otherwise, the battery could freeze.
SPECIFIC GRAVITY (EXCEPT MAINTENANCE-FREE BATTERIES)
See Figures 2 and 3
On a maintenance-free sealed battery, a built-in eye is used for checking the specific gravity readings. Refer to the battery case for further instructions.
At least once a year, check the specific gravity of the battery. It should be 1.26-1.28 at room temperature.
The specific gravity can be checked with the use of a hydrometer, an inexpensive instrument available from many sources, including auto parts stores. The hydrometer has a squeeze bulb at one end and a nozzle at the other. Battery electrolyte is sucked into the hydrometer until the float is lifted from its seat. The specific gravity is then read by noting the position of the float. Generally, if, after charging, the specific gravity of any two cells varies more than 50 points (0.50), the battery is bad and should be replaced.
It is not possible to check the specific gravity in this manner on sealed (maintenance-free) batteries. Instead, the indicator built into the top of the case must be relied on to display any signs of battery deterioration. If the indicator is a light color, the battery can be assumed to be OK. If the indicator is a dark color, the specific gravity is low, and the battery should be charged or replaced.
CABLES AND CLAMPS
See Figures 4, 5, 6 and 7
Once a year, the battery terminals and the cable clamps should be checked and cleaned, if necessary. Loosen the clamps and remove the cables, negative cable first. On batteries with posts on top, the use of a puller specially made for this purpose is recommended. These are inexpensive, and available in most auto parts stores. Side terminal battery cables are secured with a bolt.
Clean the cable clamps and the battery terminal with a wire brush, until all corrosion, grease, etc., is removed and the metal is shiny. It is especially important to clean the inside of the clamp thoroughly, since a small deposit of foreign material or oxidation there will prevent a sound electrical connection and inhibit either starting or charging. Special tools are available for cleaning these parts, one type for top post batteries and another type for side terminal batteries.
Before installing the cables, loosen the battery hold-down clamp or strap, remove the battery and check the battery tray. Clear it of any debris, and check it for soundness. Rust should be wire brushed away, and the metal given a coat of anti-rust paint. Install the battery and tighten the hold-down clamp or strap securely, but be careful not to overtighten, as doing so may crack the battery case.
After the clamps and terminals are clean, reinstall the cables, negative cable last; do not hammer on the clamps to install. Tighten the clamps securely, but do not distort them. Give the clamps and terminals a thin external coat of grease after installation, to retard corrosion.
Check the cables at the same time that the terminals are cleaned. If the cable insulation is cracked or broken, or if the ends are frayed, the cable should be replaced with a new cable of the same length and gauge.
See Figures 8, 9 and 10
When it becomes necessary to replace the battery, be sure to select a new battery with a cold cranking power rating equal to or greater than the battery originally installed. Deterioration, embrittlement and just plain aging of the battery cables, starter motor and associated wires makes the battery's job all the more difficult in successive years. The slow increase in electrical resistance over time makes it prudent to install a new battery with a greater capacity than the old. Details on battery removal and installation are covered in Engine & Engine Overhaul .