ELECTRICAL STARTING SYSTEM
The electrical system on the engine generally consists of a battery-charging alternator, a starting motor, voltage
regulator, storage battery, starter switch and the necessary wiring. Additional electrical equipment may be installed on
the engine unit at the option of the owner.
The starting motor has a Sprag overrunning clutch. Pressing the starting switch engages the starting motor pinion with
the teeth of the flywheel ring gear and energizes the starting motor. The starting motor drives the pinion and rotates the
crankshaft. When the engine begins to operate, the Sprag clutch permits the pinion to overrun on its shaft, until the
starting switch is released, and prevents overspeeding the starting motor.
To start the engine, a switch is used to energize the starting motor. Release the switch immediately after the engine
The battery-charging alternator provides the electrical current required to maintain the storage battery in a charged
condition and to supply sufficient current to carry any other electrical load requirements up to the rated capacity of the
A voltage regulator is introduced into the electrical system to regulate the voltage and current output of the battery-
charging alternator and to maintain a fully charged storage battery.
The lead-acid storage battery is an electrochemical device for converting chemical energy into electrical energy.
The battery has three major functions:
It provides a source of electrical power for starting the engine.
It acts as a stabilizer to the voltage in the electrical system.
It can, for a limited time, furnish current when the electrical demands of the unit exceed the output of the alternator.
The battery is a perishable item which requires periodic servicing. A properly cared for battery will give long and trouble-
Check the level of the electrolyte regularly. Add water if necessary, but do not overfill. Overfilling can cause poor
performance or early failure.
Keep the top of the battery clean. When necessary, wash with a baking soda solution and rinse with fresh water.
Do not allow the soda solution to enter the cells.
Inspect the cables, clamps and hold-down bracket regularly. Clean and re-apply a light coating of grease when
needed. Replace corroded, damaged parts.
Use the standard, quick in-the-unit battery test as the regular service test to check battery condition.
Check the electrical system if the battery becomes discharged repeatedly.
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 check the level of the electrolyte regularly. The Lubrication and Preventive
Maintenance section of this manual covers the servicing of the starting motor and alternator.
Consult an authorized Detroit Diesel Allison Service Outlet for information regarding the electrical system.