TM 5-3895-346-14
BATTERY-CHARGING ALTERNATOR
ENGINE OVERHAUL
ALTERNATOR PRECAUTIONS
Precautions must be taken when working on or around alternators. The diodes and transistors in the alternator
circuit are very sensitive and can be easily destroyed.
Avoid grounding or shorting the output wires or the field wires between the alternator and the regulator. Never
run an alternator on an open circuit.
Grounding an alternator's output wire or terminals, which are always "hot" regardless of whether or not the
engine is running or accidental reversing of the battery polarity will destroy the diodes. Grounding the field
circuit will also result in the destruction of the diodes. Some voltage regulators provide protection against some
of these circumstances. However, it is recommended that extreme caution be used.
Accidentally reversing the battery connections must be avoided.
Never disconnect the battery while an alternator is in operation. Disconnecting the battery will result in damage
to the diodes due to the momentary high voltage and current generated by the rapid collapse of the magnetic
field surrounding the field windings.
If a booster battery is to be used, the batteries must be connected correctly (negative to negative and positive
to positive).
Never use a fast charger with the battery connected or as a booster for battery output.
Never attempt to polarize the alternator.
The alternator diodes are also sensitive to heat and care must be exercised to prevent damage to them from
soldering irons, etc.
If faulty operation of an alternator occurs on an engine equipped with an insulated starting motor, check to be
sure that a ground strap is present and is correctly installed.
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