Charging System - Service Information: Overview RAM Cab & Chassis 3500 HD

DESCRIPTION

The charging system consists of

1. Generator
2. Electronic Voltage Regulator (EVR) circuitry within the Powertrain Control Module (PCM).
3. Ignition switch
4. Battery. For information, refer to «BATTERY»(ref-476509-S00921766152012060400000) .
5. Battery temperature sensor
6. Check Gauges Lamp (if equipped)
7. Voltmeter. For information, refer to appropriate Electrical Diagnostic article.
8. Wiring harness and connections. For information, refer to appropriate wiring information.

Scheme 33

The charging system is turned on and off with the Powertrain Control Module (PCM) and ignition switch with engine running. The field circuit will not be energized until engine is running and ignition switch on. This voltage is connected through the PCM and supplied to one of the generator field terminals (Gen. Source B+) at the back of the generator. The generator is internally grounded. The generator regulates the field using pin-1 of the field connector (high side driver).

The generator is driven by the engine through a serpentine belt and pulley, or a decoupler pulley arrangement.

The PCM receives a voltage input from the generator (5) and also a battery voltage input (7) from the Totally Integrated Power Module (TIPM), it then compares the voltages to the desired voltage programed in the Electronic Voltage Regulator (EVR) software, and, if there is a difference it sends a signal to the generator EVR circuit to increase or decrease output. It uses a Pulse Width Modulation (PWM) to send signals to the generator circuitry to control the amount of output from the generator. The amount of DC current produced by the generator is controlled by the EVR circuitry contained within the generator.

All vehicles are equipped with On-Board Diagnostics (OBD). All OBD-sensed systems, including EVR circuitry, are monitored by the PCM. Each monitored circuit is assigned a Diagnostic Trouble Code (DTC). The PCM will store a DTC in electronic memory for certain failures it detects.

The Check Gauges Lamp (if equipped) monitors: charging system voltage, engine coolant temperature and engine oil pressure. If an extreme condition is indicated, the lamp will be illuminated. This is done as reminder to check the three gauges. The lamp is located on the instrument panel.

Voltage is monitored at the B+ terminal stud to insure it is connected. If the B+ cable is loose, the PCM will shut down generator field. Because of this new feature, pin-2 of the field connector is internally connected to the B+ terminal.

The generator is belt-driven by the engine using a serpentine type drive belt. It is serviced only as a complete assembly. If the generator fails for any reason, the entire assembly must be replaced.

OPERATION

As the energized rotor begins to rotate within the generator, the spinning magnetic field induces a current into the windings of the stator coil. Once the generator begins producing sufficient current, it also provides the current needed to energize the rotor.

The stator winding connections deliver the induced alternating current to 3 or 6 positive and 3 or 6 negative diodes for rectification. From the diodes, rectified direct current is delivered to the vehicle electrical system through the generator battery terminal.

Although the generators appear the same externally, different generators with different output ratings are used on this vehicle. Be certain that the replacement generator has the same output rating and part number as the original unit. For amperage ratings, refer to GENERATOR RATINGS .

Noise emitting from the generator may be caused by: worn, loose or defective bearings; a loose or defective drive pulley; incorrect, worn, damaged or misadjusted fan drive belt; loose mounting bolts; a misaligned drive pulley or a defective stator or diode.

Scheme 34

Scheme 35

1. Disconnect the negative battery cable.
2. Remove the generator drive belt. Refer to «BELT, SERPENTINE, REMOVAL»(ref-476513-S39681365202012060400000).
3. Unsnap the plastic insulator cap from the B+ output terminal (3). (Scheme 34)
4. Remove the B+ terminal mounting nut at the rear of generator (2). (Scheme 34) Disconnect the terminal from the generator.
5. Disconnect the field wire connector at the rear of the generator (4) by pushing on the connector tab. (Scheme 34) 1 - LOWER BOLTS 2 - REAR BOLT 3 - GENERATOR
6. Remove the one rear vertical generator mounting bolt (2). (Scheme 35)
7. Remove the two front horizontal generator mounting bolts (1). (Scheme 35)
8. Remove the generator from vehicle.

Scheme 36

Scheme 37

1. Disconnect the negative battery cable.
2. Remove the generator drive belt. Refer to «BELT, SERPENTINE, REMOVAL»(ref-476513-S39681365202012060400000).
3. Unsnap the plastic insulator cap from the B+ output terminal.
4. Remove the B+ terminal mounting nut at the rear of the generator. Disconnect the terminal from the generator.
5. Disconnect the field wire connector at the rear of generator by pushing on the connector tab.
6. Remove the generator support bracket nuts (3) and bolt (4) and remove the support bracket. (Scheme 36) 1 - MOUNTING BOLT 2 - GENERATOR 3 - MOUNTING STUD / BOLT
7. Remove the two generator mounting bolts (1) and (3). (Scheme 37)
8. Remove the generator from the vehicle.

Scheme 38

Scheme 39

1. Disconnect both negative battery cables at both batteries.
2. Remove generator drive belt. Refer to «BELT, SERPENTINE, REMOVAL»(ref-476513-S39681365202012060400000).
3. Remove upper mounting bracket bolt (2). (Scheme 38)
4. Remove lower mounting bracket bolt and nut (2). (Scheme 38)
5. Remove generator from engine. 1 - B+ CONNECTOR 2 - GENERATOR 3 - FIELD WIRE CONNECTOR
6. Unsnap plastic insulator cap (1) from B+ output terminal.
7. Remove B+ terminal mounting nut at rear of generator. Disconnect terminal from generator.
8. Disconnect field wire connector (3) at rear of generator by pushing on connector tab.

The Electronic Voltage Regulator (EVR) is not a separate component. It is actually a voltage regulating circuit located within the PCM (Powertrain Control Module). The EVR is not serviced separately. If replacement is necessary, the PCM must be replaced.

The amount of direct current produced by the generator is controlled by EVR circuitry contained within the PCM. This circuitry is connected in series with the generators second rotor field terminal and its ground.

Voltage is regulated by cycling the battery positive path to control the strength of the rotor magnetic field. The EVR circuitry monitors system line voltage (B+) and battery temperature (refer to appropriate Electrical Diagnostic article). It then determines a target charging voltage. If sensed battery voltage is 0.5 volts or lower than the target voltage, the PCM grounds the field winding until sensed battery voltage is 0.5 volts above target voltage. A circuit in the PCM cycles the battery positive (high side) of the generator field up to 400 times per second (400Hz), but has the capability to ground the field control wire 100% of the time (full field) to achieve the target voltage. If the charging rate cannot be monitored (limp-in), a duty cycle of 25% is used by the PCM in order to have some generator output. For additional information, refer to OPERATION .