Most of the testing of the electrical system can be
done on the engine. The wiring insulation must be in
good condition, the wire and cable connections clean
and tight and the battery fully charged. If on the engine
test shows a defect in a component remove the
component for more testing.
5P300 Electrical Tester.
9S1990 or 1P7400 Battery Charger Tester.
5P957 or 5P3414 Coolant and Battery Tester.
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 charging
unit are broken while the charging unit is charging. 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
9S1990 BATTERY CHARGER TESTER
Never disconnect any charging unit circuit
battery circuit cable from battery when charging
unit is charging.
Load test a battery that does not hold a charge when
in use. To do this, put a resistance, across battery
main connections (terminals). For a 6 volt battery, put a
resistance of two times the ampere/hour rating of the
battery. For a 12 volt battery, put
a resistance of three times the ampere/ hour rating. Let
the resistance remove the charge (discharge battery) for
15 seconds. Immediately test the battery voltage. A 6
volt battery in good condition test 4.5 volts; a 12 volt
battery in good condition will test 9 volts.
5P300 Electrical Tester.
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 always in a low condition of charge or a large amount
of water is needed (one ounce per cell per week or every
50 service hours)
Test the charging units and voltage regulators on the
engine, when possible, using wiring and components
that are a permanent part of the system. Off the engine
(bench) testing will give an operational test of the
charging unit and voltage regulator. This testing will give
an indication of needed repair. Final testing will give
proof that the units are repaired to their original operating
Before starting on the engine testing, the charging
system and battery must be checked. See the following
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
Cables between the battery, starter and engine
ground must be the correct size. Wires and
cables must be free of corrosion and have cable
support clamps to prevent stress on battery
instruments that have direct relation to the
charging circuit must give proper circuit control.
Inspect the drive components for the charging
unit to be sure they are free of grease and oil
and are able to drive the load of the charging