PULLEY A. 7M4754 - Caterpillar

2P1204 Alternator
2P1204 Alternator
(1) Brush assembly. (2) Stator. (3) Rotor. (4) Roller bearing (5) Slip rings. (6) Ball bearings.The alternator is driven by V belts from the crankshaft pulley. It is a 24 volt, 19 ampere unit with a regulator which has no moving parts (solid state) installed on the side opposite the pulley. The alternator made up of a head assembly on the drive end, rotor assembly, stator assembly, rectifier and heat removal assemblies, brush and holder assembly, head assembly on the ring end, and regulator.The rotor assembly has the field windings (wires around an iron core) which make magnet-like lines of force when direct current (DC) flows through them. As the rotor turns, the magnet-like lines of force are broken by the stator. This makes an alternating current (AC) in the stator. The rectifier has diodes which change the alternating current (AC) from the stator to direct current (DC). Most of the direct current (DC) does to charge the battery and make a supply of direct current (DC) for the low amperage circuit. The remainder of the direct current (DC) is sent to the field findings through the brushes.Alternator Regulators
The voltage regulator is a solid state electronic switch. It feels the voltage in the system and gives the necessary field current (current to the field windings of the alternator) for the alternator to make the needed voltage. The voltage regulator controls the field current to the alternator by switching on and off many times a second. There is no voltage adjustment for these regulators.Starting System Components
Solenoid
Typical Solenoid SchematicA solenoid is a magnetic switch that does two basic operations. a. Closes the high current starter motor circuit with a low current start switch circuit.b. Engages the starter motor pinion with the ring gear.The solenoid switch is made of an electromagnet (one or two sets of windings) around a hollow cylinder. There is a plunger (core) with a spring load inside the cylinder that can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic field is made that pulls the plunger forward in the cylinder. This moves the shift lever (connected to the rear of the plunger) to engage the pinion drive gear with the ring gear. The front end of the plunger then makes contact across the battery and motor terminals of the solenoid, and the starter motor begins to turn the flywheel of the engine.When the start switch is opened, current no longer flows through the windings. The spring now pushes the plunger back to the original position, and at the same time, moves the pinion gear away from the flywheel.When two sets of windings in the solenoid are used, they are called the hold-in windings and the pull-in winding. Both have the same number of turns around the cylinder, but the pull-in winding uses a larger diameter wire to produce a greater magnetic field. When the start switch is closed, part of the current flows from