- Charging circuit
- Starting circuit
- Low amperage circuit
The following electrical system components may be used in more than one circuit:
- Battery (batteries)
- Disconnect switch
- Circuit breaker
- Ammeter
- Cables from the battery
- Wires from the battery
The charging circuit is in operation when the engine is running. An alternator generates electricity for the charging circuit. A voltage regulator in the circuit controls the electrical output due to the need 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 machine contains a disconnect switch, the starting circuit can operate only after the disconnect switch is moved to the ON position.
The starting circuit is in operation only when the start switch is activated.
Both the low amperage circuit and the changing circuit are connected to the same side of the ammeter. The starting circuit connects to the opposite side of 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. |
Alternator
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| Illustration 1 | g00317606 |
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 belts from the crankshaft pulley. This alternator is a three-phase, self-rectifying charging unit. The regulator is part of the alternator.
This alternator design does not need slip rings or brushes. The only part that moves is the rotor assembly. All conductors that carry current are stationary.
A list of the conductors follows:
- Field winding
- Stator windings
- Six rectifying diodes
- Regulator circuit components
The rotor assembly contains many magnetic poles. These magnetic poles look like fingers with air space between each of the opposite poles. The poles have residual magnetism that is similar to permanent magnets. Permanent magnets produce a small amount of magnetic lines of force (magnetic field) 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. This alternate current is generated in the stator windings from the small, magnetic lines of force. The magnetism of the pole creates the magnetic lines of force.
This alternating current (AC) is changed to direct current (DC) when the alternating current (AC) passes through the diodes of the rectifier bridge. Most of this current accomplishes these two activities:
- The current charges the battery.
- The current supplies the low amperage circuit.
The remainder is sent to the field windings.
The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force. These stronger lines of force increase the amount of alternating current (AC) 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 switch. These electronic switches operate in this manner:
- A voltage regulator feels the voltage in the system.
- A voltage regulator rapidly alternates between the ON position and the OFF position. This allows the voltage regulator to control the field current (DC current to the field windings) for the alternator.
- A voltage regulator alternates rapidly at many times per second.
In this manner, the voltage regulator allows the alternator to meet the needed voltage output.
Alternator Regulator
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| Illustration 2 | g00317610 |
Alternator Regulator (Typical Example) | |
The alternator regulator is an electronic switch. This regulator feels the voltage in the system. Next, the voltage regulator provides the necessary field current (current to the field windings of the alternator) for the alternator. This allows the alternator regulator to generate the needed voltage.
The alternator regulator rapidly alternates between the ON position and the OFF position.
Starting System Components
Solenoid
 | |
| Illustration 3 | g00317613 |
Typical Solenoid Schematic | |
A solenoid is a magnetic switch that performs two basic operations:
- A solenoid closes the high current starting motor circuit with a low current start switch circuit.
- A solenoid engages the starting motor pinion with the ring gear.
The solenoid switch has an electromagnet. The electromagnet consists of one set of windings around a hollow cylinder or of two sets of windings around a hollow cylinder. There is a plunger (core) with a mechanical spring load inside the hollow cylinder. The plunger can move forward and backward.
When the start switch closes and electricity is sent through the windings, a magnetic field is created. The magnetic field pulls the plunger forward in the cylinder. This causes the shift lever, that is connected to the plunger's rear, to engage the pinion drive gear with ring gear. The front end of the plunger then makes contact across the battery and across the terminals of the solenoid. Now, the starting motor begins to turn the engine flywheel.
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 hollow cylinder. Then, the shift lever that is connected to the rear of the plunger moves.
This causes the pinion drive gear to engage with the ring gear. The front end of the plunger contacts points across both the battery and motor terminals of the solenoid. Then, the starting motor begins to turn the flywheel of the engine.
When the start switch is opened, the current no longer flows through the winding. The spring now pushes the plunger back to the original position. At the same time, this movement pushes the pinion gear away from the flywheel.
When two sets of windings in the solenoid are used, these sets are called:
- Hold-in windings
- Pull-in windings
Both windings contain the same number of turns around the hollow cylinder. However, the pull-in windings use a larger diameter of wire to produce a greater magnetic field.
When the start switch is closed, part of the current flows from the battery through the hold-in windings. The rest of the current flows through the pull-in windings and to motor's terminal. Finally, the rest of the current flows through the motor to ground.
When the solenoid is fully activated, the connection across the battery is complete and the connection across the motor terminal is complete. Therefore, the current is shut off through the pull-in windings.
Now, only the smaller hold-in windings are in operation for the extended period of time that is required to start the engine. The solenoid draws less current from the battery. The heat that is generated by the solenoid remains at an acceptable level.
Starting Motor
The starting motor is used to turn the engine flywheel at a rate that is fast enough to start running the engine.
 | |
| Illustration 4 | g00292330 |
Cross Section of Starting Motor (1) Field winding. (2) Solenoid. (3) Clutch. (4) Starting motor pinion. (5) Commutator. (6) Brush assembly. (7) Armature. | |
The starting motor contains a solenoid. When the start switch is activated, the solenoid will move starting motor pinion (4). Then, this pinion engages the ring gear on the flywheel of the engine. Starting motor pinion (4) engages with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starting motor.
When the circuit between the battery and the starting motor is complete, the starting motor pinion will turn the engine flywheel. A clutch provides protection for the starting motor so that the engine cannot turn the starting motor too fast. When the start switch is released, the starting motor pinion will move away from the ring gear.
Other Components
Circuit Breaker
 | |
| Illustration 5 | g00281837 |
Circuit Breaker Schematic (1) Reset button. (2) Metal disc in open position. (3) Contacts. (4) Metal disc. (5) Battery circuit terminals. | |
The circuit breaker is a switch that opens the battery circuit if the current in the electrical system rises higher than the rating of the circuit breaker.
A metal disc with a contact point is activated by heat. A metal disc with a contact point completes the electric circuit through the circuit breaker.
If the current in the electrical system climbs too high, the current causes (4) metal disc to become hot. This heat causes a distortion of the metal disc that opens the contacts. This breaks the circuit. An open circuit breaker can be reset after the open circuit breaker becomes cool. This allows an adjustment to make the circuit complete again. Push the reset button in order to close the contacts. This resets the circuit breaker.
Wiring Diagrams
Many types of electrical systems are available for these engines. Some charging systems use an alternator and a regulator in the wiring circuit. Other charging systems have the regulator inside the alternator. Other starting systems use air starting motors.
A fuel pressure switch is used in all systems with an external regulator. The switch prevents current discharge (field excitation) to the alternator from the battery when the engine is not in operation. In systems that have the regulator as part of the alternator, the transistor circuit prevents current discharge to the alternator and the fuel pressure switch is not required.
All wiring schematics are usable with 12, 24, 30 or 32 volts unless the wiring schematics are specifically noted.
Note: Automatic Start/Stop systems are different wiring diagrams. Refer to the Service Manual for more information on engine attachments.
Table 1 gives the correct sizes and color codes.
| Color Code | Total Maximum Recommended Length of the Battery Cable | Wires that are Marked #X | |||
| B-Black | Cable Size | Electric Starting | Output of the Charging Unit | Wire Size | |
| W-White | 12 Volt | 24 to 32 Volt | 0 to 18 amp | #14 | |
| R-Red | 0 | 4.0 ft | 15.0 ft | 19 to 30 amp | #10 |
| O-Orange | 00 | 5.0 ft | 18.0 ft | 31 to 45 amp | #8 |
| BR-Brown | 000 | 6.0 ft | 21.0 ft | 46 to 65 amp | #6 |
| LT GN-Light Green | 0000 | 7.5 ft | 27.0 ft | 66 to 105 amp | #4 |
| PU-Purple | The number that is following the color code is the wire size that is recommended. | ||||
| W/B-White with Black Stripe | |||||
Grounded Electrical Systems
These systems are used in applications when it is not necessary to prevent radio distortion and/or chemical changes (electrolysis) of grounded components.
Regulator Inside the Alternator
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| Illustration 6 | g00499162 |
Charging System (1) Ammeter. (2) Alternator. (3) Battery. | |
 | |
| Illustration 7 | g00493528 |
Charging System with Electric Starting Motor (1) Start switch (2) Ammeter (3) Alternator (4) Battery (5) Starting motor | |
Regulator that is Separate from the Alternator
 | |
| Illustration 8 | g00493529 |
Charging System (1) Ammeter (2) Regulator (3) Battery (4) Pressure switch (5) Alternator | |
 | |
| Illustration 9 | g00499175 |
Charging System with the Electric Starting Motor (1) Start switch (2) Ammeter (3) Regulator (4) Starting motor (5) Battery (6) Pressure switch (7) Alternator | |
Starting Systems
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| Illustration 10 | g00493532 |
Starting System (1) Start switch. (2) Starting motor. (3) Battery. | |
Insulated Electrical Systems
These systems are most often used in applications when it is necessary to prevent radio distortion and/or chemical changes (electrolysis) of grounded components.
Regulator Inside the Alternator
 | |
| Illustration 11 | g00493533 |
Charging System (1) Ammeter (2) Alternator (3) Battery | |
 | |
| Illustration 12 | g00493534 |
Charging System with Electric Starting Motor (1) Start switch (2) Ammeter (3) Alternator (4) Battery (5) Starting motor | |
Regulator that is Separate from the Alternator
 | |
| Illustration 13 | g00493535 |
Charging System (1) Ammeter (2) Regulator (3) Battery (4) Pressure switch (5) Alternator | |
 | |
| Illustration 14 | g00493537 |
Charging System with the Electric Starting Motor (1) Start switch (2) Ammeter (3) Regulator (4) Starting motor (5) Battery (6) Pressure switch (7) Alternator | |
Starting Systems
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| Illustration 15 | g00493538 |
Starting System (1) Start switch. (2) Starting motor. (3) Battery. | |