Engine Electrical System
The electrical system has two separate circuits.
- the charging circuit
- the starting circuit
Some of the electrical system components are used in more than one circuit. The following items are common in each of the circuits.
- The battery
- The circuit breaker
- The cables
- The wires for the battery
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 in order to keep the battery at full charge.
| NOTICE |
|---|
The disconnect switch, if so equipped, must be in the ON position to let the electrical system function. There will be damage to some of the charging circuit components if the engine runs with the disconnect with in the OFF position. |
If the engine has a disconnect switch, the starting circuit can operate only after the disconnect switch is put in the "ON" position.
The starting switch 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
| NOTICE |
|---|
Never operate the alternator without the battery in the circuit. Making or breaking an alternator connection with heavy load on the circuit can cause damage to the regulator. |
5N-5692 Alternator
 | |
| Illustration 1 | g01247051 |
5N-5692 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 the crankshaft pulley through a belt that is a Poly-vee type. This alternator is a three-phase self-rectifying charging unit. The regulator is part of the alternator.
This alternator design has no need for slip rings or for brushes. The only part of this alternator that moves is the rotor assembly. All of the conductors that carry current are stationary. The following components are the conductors: the field winding, the stator windings, six rectifying diodes and the regulator circuit.
The rotor assembly has many magnetic poles. The magnetic poles are similar to fingers. An air space exists between each of the opposite poles. The poles have residual magnetism that produces a small amount of magnet-like lines of force (magnetic field). This magnetic field is produced between the poles. As the rotor assembly begins to turn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings. The alternating current is produced from the small magnetic lines of force that are created by the residual magnetism of the poles. The AC is changed into direct current (DC) when the current passes through the diodes of the rectifier bridge. Most of this current provides the battery charge and the supply for the low amperage circuit. The remainder of the current is sent to the field windings. The DC current flow through the field windings (wires around an iron core) increases the strength of the magnetic lines of force. These stronger magnetic lines of force increase the amount of AC that is produced in the stator windings. The increased speed of the rotor assembly also increases the current output of the alternator and the voltage output of the alternator.
3T-6354 Regulator Assembly
 | |
| Illustration 2 | g00360155 |
3T-6354 Regulator Assembly | |
The voltage regulator is a solid-state electronic switch. The voltage regulator senses the voltage of the system. The regulator then uses switches to control the current to the field windings. This controls the voltage output in order to meet the electrical demand of the system.
Starting System Components
Solenoid
A solenoid is an electromagnetic switch that performs two basic functions:
- The solenoid closes the high current starting motor circuit with a low current start switch circuit.
- The solenoid engages the starting motor pinion with the ring gear.
 | |
| Illustration 3 | g00292316 |
Typical solenoid schematic | |
The solenoid has windings (one set or two sets) around a hollow cylinder. A plunger with a spring load device is inside of the cylinder. The plunger can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic field is created. The magnetic field pulls the plunger forward in the cylinder. This moves the shift lever in order for the pinion drive gear to engage with the ring gear. The front end of the plunger then makes contact across the battery and across the motor terminals of the solenoid. The starting motor then begins to turn the flywheel of the engine.
When the start switch is opened, current no longer flows through the windings. The spring now returns the plunger to the original position. At the same time, the spring moves the pinion gear away from the flywheel.
When two sets of windings in the solenoid are used, the windings are called the hold-in winding and the pull-in winding. Both of the windings wind around the cylinder for an equal amount of times. The pull-in winding uses a wire with a larger diameter in order to produce a stronger magnetic field. When the start switch is closed, part of the current flows from the battery through the hold-in winding. The remainder of the current flows through the pull-in windings, to the motor terminal, and then to the ground. When the solenoid is fully activated, the current is shut off through the pull-in windings. Only the smaller hold-in windings are in operation for the extended period of time that is necessary for the engine to be started. The solenoid will now take a smaller amount of current from the battery. Heat that is created by the solenoid will be kept at an acceptable level.
Starting Motor
The starting motor rotates the engine flywheel at a rate that is fast enough to start the engine.
The starting motor has a solenoid (2). When the start switch is activated, the solenoid (2) will move the starter pinion (4) in order to engage the starter pinion (4) and the ring gear on the engine flywheel. The starter pinion (4) and the ring gear will engage before the circuit between the battery and the starting motor is closed by the electric contacts in the solenoid (2). When the circuit between the battery and the starting motor is complete, the starter pinion (4) will rotate the engine flywheel. A clutch provides protection for the starting motor so that the engine cannot turn the starting motor too fast. When the switch is released, the starter pinion (4) will move away from the ring gear.
 | |
| Illustration 4 | g01247102 |
Starting motor cross section (1) Field (2) Solenoid (3) Clutch (4) Starter pinion (5) Commutator (6) Brush assembly (7) Armature | |
Other Components
Circuit Breaker
The circuit breaker is a switch that opens the battery circuit if the current in the electrical system is higher than the rating of the circuit breaker. The metal disc (2) is activated by heat. If the current in the electrical system gets too high, the metal disc will get hot. This heat causes a distortion of the metal disc. A circuit breaker that is open can be reset when the metal disc becomes cooler. Push the reset button (1) in order to close the contact points and reset the circuit breaker.
 | |
| Illustration 5 | g01247131 |
Circuit breaker schematic (1) Reset button (2) Disc in open position (3) Contacts (4) Disc (5) Battery circuit terminals | |