A regulator is incorporated in the electrical system to
Precautions must be taken when working on or around
regulate the voltage and current output of the battery-
charging alternator and to help maintain a fully
transistors in the alternator circuit are very sensitive
charged storage battery.
and can be easily destroyed.
Avoid grounding the output wires or the field wires
between the alternator and the regulator. Never run an
alternator on an open circuit.
The lead-acid storage battery is an electrochemical
device for converting chemical energy into electrical
Grounding an alternator's output wire or terminals,
which are always hot regardless whether or not the
The battery has three major functions:
engine is running, and accidental reversing of the
battery polarity will destroy the diodes. Grounding the
1. It provides a source of electrical power for starting
field circuit will also result in the destruction of the
diodes. Some voltage regulators provide protection
against some of these circumstances. However, it is
2. It acts as a stabilizer to the voltage in the electrical
recommended that extreme caution be used.
3. It can, for a limited time, furnish current when the
Accidentally reversing the battery connections must be
electrical demands of the unit exceed the output of the
Never disconnect the battery while an alternator is in
The battery is a perishable item which requires
operation. Disconnecting the battery will result in
periodic servicing. A properly cared for battery will
damage to the diodes, due to the momentary high
give long and trouble-free service.
voltage and current generated by the rapid collapse of
the magnetic field surrounding the field windings.
1. Check the level of the electrolyte regularly. Add
water if necessary, but do not overfill. Overfilling can
cause poor performance or early failure.
In marine applications which have two sets of
batteries, switching from one set of batteries to the
2. Keep the top of the battery clean. When necessary,
other while the engine is running will momentarily
wash with a baking soda solution and rinse with fresh
disconnect the batteries and result in damage to the
water. Do not allow the soda solution to enter the cells.
3. Inspect the cables, clamps and hold-down bracket
If a booster battery is to be used, the batteries must be
regularly. Clean and re-apply a light coating of grease
connected correctly (negative to negative and positive
when needed. Replace corroded, damaged parts.
4. Use the standard, quick in-the-unit battery test as
the regular service test to check battery condition.
Never use a fast charger with the battery connected, or
as a booster for battery output.
5. Check the electrical system if the battery becomes
not necessary and is harmful.
If the engine is to be stored for more than 30 days,
remove the battery. The battery should be stored in a
cool, dry place. Keep the battery fully charged and
The alternator diodes are also sensitive to heat, and
check the level of the electrolyte regularly.
care must be exercised to prevent damage to them
The Lubrication and Preventive Maintenance section of
this manual covers the servicing of the starting motor
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
Consult an authorized Detroit Diesel Allison Service
Outlet for information regarding the electrical system.