Chapter 22 Basic Electrical Tests 345
Using an Inductive Wire Tracer
An inductive wire tracer uses a signal generator and
an inductive pickup to fi nd shorts. See Figure 22-15A.
The signal generator is connected to the vehicle bat-
tery as shown in Figure 22-15B or to the battery and to
the affected circuit. This produces a weak, fl uctuating
voltage in the wiring. The pickup, or detector, can then
be moved along the outside of the wiring as shown in
Figure 22-15C. It senses the fl uctuating magnetic fi eld
around the outside of the wire. If you move the sensor
over a short in the wire, the audible tone changes or
the tracer makes a beeping sound, depending on the
particular tracer.
Using a Multimeter
A multimeter is a voltmeter, ammeter, and
ohmmeter combined in one housing. Also called
a VOM (volt-ohm-milliammeter), it is an essential
tool for automotive technicians. It can make accu-
rate measurements of circuit values, which you
can compare to known good values. If the mea-
sured values are high or low, you know a problem
exists in the circuit.
Figure 22-12. If the test light glows dimly, you have a high
resistance or poor electrical connection in the circuit. A—A
test light is being used to check for power to the power window
switch. B—The test light has a sharp, pointed tip. It can be
touched on a terminal or pushed through wire insulation to
touch the conductor.
Figure 22-13. To use a self-powered test light, you must fi rst
disconnect the circuit power source.
Figure 22-14. Using a test light to help fi nd a short circuit.
Remember to disconnect the circuit before testing if you are
using a self-powered test light.
Connector to
power window switch
Grounded test light
A
Pierce insulation to touch
conductor—keep fingers
out of the way!
Touch probe on
metal terminal
through outside
of connector
B
M
Battery
Switch
Motor
If self-powered
test light glows,
path is complete
Fuse
Wire or component
is isolated from
power source
Fuse block
(fuse removed)
Short to
ground
Load
disconnected
Load
Switch
Test light glows
until short is found