resistance in these circuits reduces the overall charge
rate and leads to eventual battery discharge.
The external volts lead is connected to the generator
armature terminal, as shown in figure 4-11, when a
generator is tested and to the battery terminal when an
alternator is tested.
If a voltage loss exceeds the specified amount for
the unit being tested, an excessive resistance is present
within the charging system; that is, within the wiring
harness, connections, regulator, and vehicle ammeter
(if used). The excessive resistance might take the form
of LOOSE or CORRODED CONNECTIONS at the
output terminal of the generator or alternator, the
armature terminal of the regulator, or the back of the
ammeter or battery terminal of the starter solenoid
battery cable connections. Excessive resistance can
also be due to faulty wiring from generator to
regulator, regulator to ammeter, or ammeter to starter
solenoid; to burned or oxidized cutout relay contacts
within the regulator; or to poor electrical connections
between the generator or alternator and the engine. To
isolate the point of excessive resistance, conduct a
charging system insulated circuit resistance test.
generator armature terminal or to the battery
terminal. (See fig. 4-12.) Remember to reverse the
external volts lead for positive ground systems.
Start the engine and adjust its speed to
approximately 2,000 rpm. Then adjust the load
increase knob until the AMMETER scale indicates
a current of 20 amperes for dc systems or 10
amperes for ac systems. Also observe the voltage
reading on the (3-volt) VOLTMETER scale and
compare it with the specifications for proper
charging system operation, as required by the
vehicle manufacturer. If the reading is within
specification, you should proceed with a charging
system ground circuit resistance test.
CHARGING SYSTEM INSULATED
CIRCUIT RESISTANCE TEST
You can conduct a charging system insulated
circuit resistance test by setting the volt range
selector knob to the -0.3 to 3.0 volt scale position.
When you test an alternator, observe the polarity,
and connect the external volts lead to the
Figure 4-11.-Circuit resistance test.
Figure 4-12.-Insulated circuit resistance test.