Component Tests and General Diagnostics

Battery electrolyte level, checking






- check that electrolyte covers battery plates (including separators) by 5 mm (1/4 in)
- check battery electrolyte level indicator on side of battery

Note: Only use distilled water when refilling battery

Battery condition, checking

Note: Weak battery can be caused by:
alternator belt slipping (replace belt when glazed)
ground straps corroded,
loose or broken alternator or voltage regulator defective
alternator warning light bulb burned out
poor ground connection between warning light socket and circuit board

Battery terminals and cables should be coated with grease or petroleum jelly and, if necessary, cleaned to prevent corrosion and ensure good connection

Visual checks

- check for:

cracked or leaking case
loose or corroded terminals
low electrolyte level. If electrolyte is low, refill with distilled water and fast charge battery for several minutes after cells begin gassing (boiling)

Hydrometer test (for batteries with removable caps)

- test electrolyte in all cells
average specific gravity should be at least 1.225






- correct for electrolyte temperature if necessary
for every 10°F above 80°F add 0.004 to hydrometer reading
for every 10°F below 80°F subtract 0.004 from hydrometer reading

- if specific gravity is above 1.225, load test battery
- if specific gravity is below 1.225, recharge battery
- if specific gravity varies by more than 0.050 between cells, replace battery

Caution: Do not expose fully discharged battery to freezing temperature because battery will be damaged by freezing

Voltage test-engine not running (for sealed batteries only)

- turn headlights on high beam for 1 minute to remove surface charge
- disconnect battery ground strap
- check battery voltage with an accurate voltmeter
voltage should be at least 12.4 volts






- if battery is above 12.4 volts, load test battery
- if battery is below 12.4 volts, charge battery until voltage is at least 12.4 volts

Load test

Note: Before load testing, battery must be at least 75% charged

- connect load tester according to manufacturer's instructions
- load battery to 3 times amp/hour rating or 1/2 0°F cold cranking current rating
- wait 15 seconds and read voltage
battery voltage at room temperature should be at least 9.6 volts

- if battery voltage at room temperature is below 9.6 volts, replace battery






- if battery is colder than room temperature, voltage under load will be lower. Use table if cold battery must be tested