Man,what a mess. Looks like a short somewhere but heres a run down of the charging system to help you track your way through it.
The charging system consists of:
*Generator
*Electronic Voltage Regulator (EVR) circuitry within the *Powertrain Control Module (PCM). Electronic Control *Module (ECM) for diesel engines.
*Ignition switch
*Battery (refer to 8, Battery for information)
*Battery temperature sensor
*Check Gauges Lamp (if equipped)
*Voltmeter (refer to 8, Instrument Panel and Gauges for information)
*Wiring harness and connections (refer to 8, Wiring Diagrams for information)
The Battery Temperature Sensor (BTS) is used only on the diesel engine. It is attached to the battery tray located under the battery.
The BTS is used to determine the battery temperature and control battery charging rate. This temperature data, along with data from monitored line voltage, is used by the PCM (ECM Diesel) to vary the battery charging rate. System voltage will be higher at colder temperatures and is gradually reduced at warmer temperatures.
The PCM sends 5 volts to the sensor and is grounded through the sensor return line. As temperature increases, resistance in the sensor decreases and the detection voltage at the PCM increases.
The BTS is also used for OBD II diagnostics. Certain faults and OBD II monitors are either enabled or disabled, depending upon BTS input (for example, disable purge and enable Leak Detection Pump (LDP) and O2 sensor heater tests). Most OBD II monitors are disabled below 20°F.
On diesel powered engines, the charging system is turned on and off with the ECM (Engine Control Module) and ignition switch with engine
The generator is driven by the engine through a serpentine belt and pulley, or a decoupler pulley arrangement.
The PCM, or ECM receives a voltage input from the generator (5) and also a battery voltage input (7) from the TIPM (Totally Integrated Power Module), it then compares the voltages to the desired voltage programed in the EVR (Electronic Voltage Regulator) 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.
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. Refer to the Instrument Cluster section for additional information.
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 used with diesel engines is internally regulated. The generator and ECM communicate for diagnostics, etc. If the generator regulator becomes disconnected from the ECM, it will still operate, but in a default mode.
INSPECTION
The PCM (Powertrain Control Module), or ECM (Diesel) monitors critical input and output circuits of the charging system, making sure they are operational. A Diagnostic Trouble Code (DTC) is assigned to each input and output circuit monitored by the On-Board Diagnostic (OBD) system. Some charging system circuits are checked continuously, and some are checked only under certain conditions.
Refer to Diagnostic Trouble Codes in; Powertrain Control Module; Electronic Control Modules for more DTC information.
To perform a complete test of the charging system, use a diagnostic scan tool. Perform the following inspections before attaching the scan tool.
1. Inspect the battery condition. Refer to 8, Battery for procedures.
2. Inspect condition of battery cable terminals, battery posts, connections at engine block, starter solenoid and relay. They should be clean and tight. Repair as required.
3. Inspect all fuses in both the fuseblock and Power Distribution Center (PDC) for tightness in receptacles. They should be properly installed and tight. Repair or replace as required.
4. Inspect generator mounting bolts for tightness. Replace or tighten bolts if required. Refer to the Generator Removal/Installation section of this group for torque specifications.
5. Inspect generator drive belt condition and tension. Tighten or replace belt as required. Refer to Belt Tension Specifications in 7, Cooling System.
6. Inspect automatic belt tensioner (if equipped). Refer to 7, Cooling System for information.
7. Inspect generator electrical connections at generator field, battery output, and ground terminal (if equipped). Also check generator ground wire connection at engine (if equipped). They should all be clean and tight. Repair as required.
The problems that stand out in the above are, 1) any loose or corroded connection including ALL grounds to the body and engine block 2) battery that is not boiling is weak and needs more voltage causing the good, fully charged battery to boil 3) the BTS for the boiling battery is bad (it should sense the high battery temp) 4) the factory insulation battery blanket is missing or damaged not allowing the high battery temperature to be seen at thE BTS (a cold weather issue) (REMEMBER IT IS UNDER THE BATTERY AND HEAT RISES) 5) boiling battery has intenal short, fails load test. 6) batterys are different sizes, types, manufacturers (they all have different quality testing for the amp rating of battery). the batterys need to be the same, made at the same place, at the same time. Many auto parts stores in-house batterys are made by different manufacturers at different times of the year. low bid gets the sale. The way the truck is wired, the generator hot is connected to the passenger (auxiliary) battery. Then the aux bat hot is connected to the drivers (primary) battery hot. From the pri bat hot the ECM checks the voltage output of the generator. The positive (hot) wire from the generator to the aux bat, the wire from the aux bat to the pri bat, the multi wire battery post clamp on the pri bat, and the pri bat to starter wire, all have a high posibility of causing the over charging of the passenger side battery.
