T h e r e a r e t w o c o m m o n c i r c u i t r e s i s t a n c e
testsinsulated resistance test and ground circuit
INSULATED RESISTANCE TEST.To
perform an insulated resistance test, connect the load
tester as described by the manufacturer. A typical
connection setup is shown in figure 2-35. Note how the
voltmeter is connected across the alternator output
terminal and positive battery terminal.
With the vehicle running at a fast idle, rotate the
load control knob to obtain a 20-amp current flow at 15
volts or less. All accessories and lights are to be turned
OFF. Read the voltmeter. The voltmeter should NOT
read over 0.7-volt drop (0.1 volt per electrical
connection) for the circuit to be considered in good
condition. However, if the voltage drop is over 0.7
volt, circuit resistance is high and a poor electrical
G R O U N D C I R C U I T R E S I S T A N C E
TEST.With the ground circuit resistance test the
voltmeter leads are placed across the negative battery
terminal and alternator housing (fig. 2-36).
The voltmeter should NOT read over 0.1 volt per
electrical connection. If the reading is higher, this
indicates such problems as loose or faulty connections,
burnt plug sockets, or other similar malfunctions.
Figure 2-35.Typical insulated resistance test setup.
Figure 2-36.Typical ground circuit resistance test setup.
REVIEW 1 QUESTIONS
How many electrical circuits are in a typical
automotive electrical system?
What component of the charging system
produces and stores electricity?
What substance is contained in apositiveplate of
a filly charged battery?
What type of gas collects at the top of a battery?
What is the specific gravity of a fully charged
What are the two methods of rating lead-acid
When mixing electrolyte, you should follow what
What battery test will determine if current is
discharging across the top of the battery?
You are performing a battery drain test using an
ammeter. What should the meter read with
everything in the vehicle turned off?
When performing a quick charge test, you should
charge the battery at 30 to 40 amps for what
minimum time period?
What are the two types of field circuits used in dc
What are the three design factors that determine
the output of a dc generator?
What two tests are used for locating shorts in the
armature of a dc generator?
What component of the alternator contains the
heat sink the diodes, the diode plate, and the
What type of alternator stator is used in high
How is alternator output reduced using an
electronic voltage regulator?
What is the most common type of voltage
regulator used on modern vehicles?
What charging system test measures the
charging systems voltage, under low output, low
What two testing devices are used to perform a
charging system test?