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Chapter Eight
Figure 8-50. DaimlerChrysler computer-regulated charging system internal field control. (DaimlerChrysler Corporation)
10 seconds, it sets a code 16 in memory and turns on the malfunction indicator lamp (MIL).
Figure 8-51.
GM ammeter. (GM Service and Parts
Operations)
Ammeter Diagnostic Trouble Codes (DTC) On late-model DaimlerChrysler vehicles, the onboard diagnostic capability of the engine control system detects charging system problems and records up to five diagnostic trouble codes (DTC) in the system memory. Some of the codes light a MIL on the instrument panel; others do not. Problems in the General Motors CS charging system cause the PCM to turn on the indicator lamp and set a single code in memory.
CHARGE/VOLTAGE/ CURRENT INDICATORS A charging system failure cripples an automobile. Therefore, most manufacturers provide some way for the driver to monitor the system operation. The indicator may be an ammeter, a voltmeter, or an indicator lamp.
An instrument panel ammeter measures charging system current into and out of the battery and the rest of the electrical system (Figure 8-51). The ammeter reads the voltage drop of the circuit. When current is traveling from the AC generator into the battery, the ammeter moves in a positive or charge direction. When the battery takes over the electrical system’s load, current travels in the opposite direction and the needle moves into the negative, or discharge, zone. The ammeter simply indicates which is doing the most work in the electrical system, the battery or the AC generator (alternator). Some ammeters are graduated to indicate the approximate current in amperes, such as 5, 10, or 20. Others simply show an approximate rate of charge or discharge, such as high, medium, or low. Some ammeters have a resistor parallel so the meter does not carry all of the current, these are called shunt ammeters. While the ammeter tells the driver whether the charging system is functioning normally, it does not give a good picture of the battery condition. Even when the ammeter indicates a charge, the current output
