ELECTRICAL SYSTEM
TESTING AND ADJUSTING
TM 5-3805-263-14&P-2
ELECTRICAL SYSTEM
Most of the tests of the electrical system can be
done on the engine. The wiring insulation must be in
good condition, the wire and cable connections must
be clean and tight. and the battery must be fully
charged. If the on engine test shows a defect in a
component. remove the component for more testing.
BATTERY
Electrical Tester.
Battery Charger Tester.
Coolant and Battery Tester.
NOTE: Make reference TM 9-6140-200-14 when
testing, checking or charging the battery.
Never disconnect any charging unit circuit or
battery circuit cable from battery when the
charging unit is operated. A spark can cause an
explosion from the flammable vapor mixture of
hydrogen and oxygen that is released from the
electrolyte through the battery outlets. Injury to
personnel can be the result.
The battery circuit is an electrical load on the
charging unit. The load is variable because of the
condition of the charge in the battery. Damage to the
charging unit will result, if the connections, (either
positive or negative) between the battery and charg-
ing unit are broken while the charging unit is charg-
ing. This is because the battery load is lost and there
is an increase in charging voltage. High voltage will
damage, not only the charging unit but also the
regulator and other electrical components.
Load test a battery that does not hold a charge
when in use. To do this, put a resistance across the
main connections (terminals) of the battery. For a
12V battery, use a test load of three times the
ampere/hour rating (the maximum test load on any
battery is 500 amperes). Let the test load remove
the charge (discharge) of the battery for 15 seconds
and, with the test load still applied, test the battery
voltage, A 12V battery will show 9V. Each cell of a
battery in good condition must show 1.6V.
CHARGING SYSTEM
The condition of charge in the battery at each
regular inspection will show if the charging system is
operating correctly. An adjustment is necessary
when the battery is constantly in a low condition of
charge or a large amount of water is needed (more
than one ounce of water per cell per week or per every
50 service hours).
Make a test of the charging unit and voltage reg-
ulator on the engine, when possible, using wiring and
components that are a permanent part of the system.
Off the engine (bench) testing will give a test of the
charging unit and voltage regulator operation. This
testing will give an indication of needed repair. After
repairs are made, again make a test to give proof that
the units are repaired to their original operating
condition.
Before starting the on engine testing, the charging
system and battery must be checked as given in the
Steps below.
1. Battery must be at least 75% (1.240 Sp. Gr.) full
charged and held tightly in place. The battery
holder must not put too much stress on the
battery.
1-75
