SHAFT 4T2111 - Caterpillar

This section covers only the main components of the electric starting and charging system. An engine may not be equipped with this system.The charging circuit is in operation when the engine is running. An alternator makes electricity for the charging circuit. A voltage regulator in the circuit controls the electrical output. The electrical output maintains the battery at full charge.
The disconnect switch, if so equipped, must be in the ON position for the electrical system to function properly. There will be damage to some of the charging circuit components if the engine runs with the disconnect switch in the OFF position.
The starting circuit is in operation only when the start switch is activated.The charging circuit is connected through the ammeter. The starting circuit is not connected through the ammeter. Charging System Components
Alternator
Illustration 1 g00292313
Delco-Remy Alternator (1) Regulator. (2) Roller bearing. (3) Stator winding. (4) Ball bearing. (5) Rectifier bridge. (6) Field winding. (7) Rotor assembly. (8) Fan.The alternator is driven by vee shaped belts from the crankshaft pulley. This alternator is a three-phase, self-rectifying charging unit, and the regulator is part of the alternator. The rotor assembly has many magnetic poles. There is a space between the opposite magnetic poles. The poles have residual magnetism which produces a small amount of magnet-like lines of force between the poles. A small amount of alternating current is produced as the rotor assembly begins to turn between the field winding and the stator windings. This alternating current is produced from the small magnetic lines of force that are created by the residual magnetism. The alternating current changes to direct current. This happens as the alternating current passes through the diodes of the rectifier bridge. Most of the current charges the battery. Some of this current supplies the low amperage circuit, and the remainder of the current is sent to the field windings. The DC current flow through the field windings increases the strength of the magnetic lines of force. The stronger lines of force increase the amount of the alternator current that is produced in the stator windings. The increased speed of the rotor assembly also increases the current and voltage output of the alternator. The voltage regulator is a solid-state electronic switch. This switch feels the voltage in the system. The switch turns on and off multiple times in a second. This controls the field current for the alternator which will produce the necessary voltage output.Starting System Components
Solenoid
A solenoid is a magnetic switch that performs two basic operations:
The solenoid closes the high current starter motor circuit with a low current start switch circuit.
The solenoid engages the starter motor pinion with the ring gear.
Illustration 2 g00292316
Typical solenoid schematicThe solenoid switch is made of an electromagnet around a hollow cylinder. There is a spring loaded plunger inside the cylinder. This plunger can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic field is created. This magnetic field pulls the plunger forward in the cylinder.