Engine Electrical System
 | |
| Illustration 1 | g00916927 |
Typical example | |
The electrical system has two separate circuits.
- Charging circuit
- 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:
- Battery
- Circuit breaker
- Cables
- Wires for the battery
The charging circuit is in operation when the engine is running. An alternator converts mechanical energy to electrical energy 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 equipped, must be in the ON position in order to let the electrical system function. There will be damage to some of the charging circuit components if the engine is running with the disconnect switch 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.
Automatic Shutdown System
Wiring Diagram for a 15 Amp Alternator
 | |
| Illustration 2 | g00916841 |
(1) Warning lamp (alternator) (2) Regulator (3) Alternator (4) Battery (5) Electric starting motor (6) Warning lamp (oil pressure) (7) Engine oil pressure switch (8) Warning lamp (coolant temperature) (9) Coolant temperature switch (10) Fuse (11) Ignition switch (12) Signal for glow plugs (13) Glow plugs (14) Fuel shutoff solenoid (15) Automatic shutdown device (16) Electrical connector (17) Delay fuse | |
Wiring Diagram for a 40 Amp Alternator
 | |
| Illustration 3 | g00916844 |
(1) Warning lamp (alternator) (2) Alternator (3) Battery (4) Electric starting motor (5) Warning lamp (oil pressure) (6) Engine oil pressure switch (7) Warning lamp (coolant temperature) (8) Coolant temperature switch (9) Fuse (10) Fuse (11) Ignition switch (12) Signal for glow plug (13) Glow plugs (14) Fuel shutoff solenoid (15) Automatic shutdown device (16) Electrical connector (17) Delay fuse | |
Wiring Diagram for a 55 Amp Alternator
 | |
| Illustration 4 | g00916845 |
(1) Warning lamp (alternator) (2) Alternator (3) Battery (4) Electric starting motor (5) Warning lamp (oil pressure) (6) Engine oil pressure switch (7) Warning lamp (coolant temperature) (8) Coolant temperature switch (9) Fuse (10) Ignition switch (11) Signal for glow plug (12) Glow plugs (13) Fuel shutoff solenoid (14) Automatic shutdown device (15) Electrical connector | |
Electrical Connector
 | |
| Illustration 5 | g00841411 |
Connector for the automatic shutdown device (typical example) (1) Ignition switch (red wire) (2) Ignition switch (orange wire) (3) Fuel shutoff solenoid (red and black wire) (4) Engine oil pressure switch (brown wire) (5) Coolant temperature switch (blue wire) (6) Ground (black wire) | |
Automatic Shutdown Conditions
The engine will shut down if the following conditions continue for more than ten seconds while you start the engine or for two seconds while you operate the engine:
Coolant temperature exceeds the following values:
- C2.2 ... 110° ± 3°C (230° ± 5°F)
Engine oil pressure falls below the following values:
- Engine oil pressure switch that is located on the valve mechanism cover ... 29 kPa (4.27 psi)
- Engine oil pressure switch that is located on the cylinder block ... 98 kPa (14.22 psi)
Note: There is no automatic shutdown for low coolant level.
Note: The capacity of the diode must be 3 Amperes with a reverse voltage of 600 volts.
Note: The rated current draw of the engine oil pressure switch is 0.42 Amperes (5 watts maximum bulb).
Note: If necessary, a delay fuse should be used for replacement.
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. |
Alternator
 | |
| Illustration 6 | g00292313 |
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. When the engine is running, the pulley rotates the shaft inside the alternator. The rotor assembly is attached to the shaft. 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.
Regulator
 | |
| Illustration 7 | g00360155 |
Typical 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
 | |
| Illustration 8 | g00292316 |
Typical solenoid schematic | |
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.
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.
Electric Starting Motor
 | |
| Illustration 9 | g00292330 |
Starting motor cross section (typical example) (1) Field (2) Solenoid (3) Clutch (4) Starter pinion (5) Commutator (6) Brush assembly (7) Armature | |
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, solenoid (2) will move starter pinion (4) in order to engage starter pinion (4) to the ring gear on the engine flywheel. Starting motor pinion (4) and the ring gear will engage when the circuit between the battery and the starting motor is closed by the electric contacts in solenoid (2). When the circuit between the battery and the starting motor is complete, 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, starter pinion (4) will move away from the ring gear.
Other Components
Circuit Breaker
 | |
| Illustration 10 | g00281837 |
Circuit breaker schematic (1) Reset button (2) Disc in open position (3) Contacts (4) Disc (5) Battery circuit terminals | |
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. Metal disc (2) is activated by heat. As the current in the electrical system increases, the temperature of metal disc (2) will increase. The heat that is caused by the excessive current will cause a distortion in metal disc (2). When a distortion occurs in metal disc (2), contacts (3) open. A circuit breaker that is open can be reset when the metal disc becomes cooler. Push reset button (1) in order to close contacts (3) and reset the circuit breaker.