D330, D333, 3304, 3306 – Electrical System

The electrical system is a combination of three separate electric circuits: the charging circuit, the starting circuit and the lighting or load circuit. Each circuit is dependent on some of the same components. The battery (batteries), ammeter, cables and wires from the battery are common in each of the three circuits.

The charging circuit is in operation when the diesel engine is operating. The electricity producing (charging) unit is a generator or alternator. A regulator in the circuit senses the state of charge in the battery and regulates the charging unit output to keep the battery fully charged.

The starting circuit operates only when the start switch is actuated.

The direct electric diesel engine starting circuit may include a glow plug for each diesel engine cylinder. The glow plugs are small heating elements in the precombustion chambers which promote fuel ignition when the engine is started in low temperatures.

The low amperage load and charging circuits are both connected on the same side of the ammeter while the starting circuit connects to the other side of the ammeter.

Alternator (Delco)


This alternator is a three phase self-rectifying charging unit.

The alternator has four main components: end frame assembly (brush end), rotor assembly, stator and shell assembly, and end frame assembly (drive end).

Regulator (Delco)
A separate regulator senses the charge condition of the battery as well as electrical system power demand and controls the alternator output accordingly by limiting the field current.

1. Hollow head screw. 2. Connector.


Alternator (Motorola)
The alternator is belt driven from the crankshaft pulley. It is a three-phase self-rectifying charging unit with three main functional parts: A rotating magnetic field (rotor) which produces flux; a stationary armature (stator) in which alternating current is induced; and stationary rectifying diodes that change alternating current to direct current.

The alternator field current is passed through brushes. The field current is in the order of 2 to 3 amperes. The rectifying diodes will pass current from the alternator to the battery or load, but will not pass current from the battery to the alternator.


Regulator (Motorola)
The separate transistorized voltage regulator is an electronic switching device. It senses the voltage in the system at the oil pressure switch and supplies the necessary field current to maintain the required system voltage. The voltage regulator has two basic “circuits.” The “load circuit” conducts positive potential from the regulator input lead, through a diode and transistor, to the regulator output lead, providing the circuit to the rotor (field) winding. The “control circuit” consists of a voltage sensitive zener diode, drive transistor and a voltage divider network. The “control circuit” directs the transistor in the “load circuit” to turn off and on at a rate that will provide the required charging voltage.

A solenoid is a magnetic switch that utilizes low current to close a high current circuit. The solenoid has an electromagnet with a movable core. There are contacts on the end of the core. The contacts are held open by a spring that pushes the core away from the magnetic center of the coil. Low current will energize the coil and form a magnetic field. The magnetic field draws the core to the center of the coil and the contacts close.

1. Coil. 2. Switch terminal. 3. Battery terminal. 4. Contacts. 5. Spring. 6. Core. 7. Component terminal.

Starting Motor
The starting motor is a device used to rotate the flywheel of an engine fast enough to start the engine.

1. Field. 2. Solenoid. 3. Clutch. 4. Pinion. 5. Commutator. 6. Brush assembly. 7. Armature.

The starting motor used with direct electric start incorporates a solenoid. The action of the solenoid engages the pinion with the ring gear on the engine flywheel, when the solenoid is energized. The pinion always engages before the electric contacts in the solenoid closes the circuit between the battery and the starting motor. An overrunning clutch protects the starting motor from being overspeeded. Releasing the start-switch disengages the pinion from the ring gear on the flywheel.

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