ROD AS 9R8972 - Caterpillar

Grounding Practices
Proper grounding for the vehicle electrical system and the engine electrical systems is necessary for proper vehicle performance and reliability. Improper grounding will result in unreliable electrical circuit paths and uncontrolled electrical circuit paths.Uncontrolled engine electrical circuit paths can result in damage to main bearings, crankshaft bearing journal surfaces, and aluminum components.Uncontrolled electrical circuit paths can cause electrical noise which may degrade the vehicle and radio performance.To ensure proper functioning of the engine electrical system, an engine-to-frame ground strap with a direct path to the battery must be used. This may be provided by a starting motor ground, by a frame to starting motor ground, or by a direct frame to engine ground. An engine-to-frame ground strap must be used in order to connect the grounding stud of the engine to the frame and to the negative battery post.
Illustration 1 g01129718
Grounding stud to battery ground ("-")
Illustration 2 g01129719
Alternate grounding stud to battery ground
The engine must have a wire ground to the battery.Ground wires or ground straps should be combined at ground studs that are only for ground use. All of the grounds should be tight and free of corrosion.The engine alternator should be battery ground with a wire size that is capable of managing the full charging current of the alternator.
When boost starting an engine, the instructions in Systems Operation, "Engine Starting" should be followed in order to properly start the engine.This engine may be equipped with a 12 volt starting system or a 24 volt starting system. Only equal voltage for boost starting should be used. The use of a higher voltage will damage the electrical system.The Electronic Control Module (ECM) must be disconnected at the "J1/P1" and "J2/P2" locations before welding on the vehicle.
Engine Electrical System
The electrical system has three separate circuits:
Charging
Starting
Low amperage accessoriesSome of the electrical system components are used in more than one circuit. The following components are common in more than one circuit:
Battery or batteries
Circuit breakers
Ammeter
Battery cablesThe 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 in order to keep the battery at full charge.
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 circuit is in operation only when the start switch is activated.Both the low amperage circuit and the charging circuit are connected to the same side of the ammeter. The starting circuit is connected to the opposite side of the ammeter.
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.