Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw

168 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).
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.
Figure 8-51.
Operations)
Ammeter
GM ammeter. (GM Service and Parts
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