Chapter 22 Basic Electrical Tests 351
CAUTION
A heat gun produces enough heat
to damage sensitive electronic
components. Use the heat gun
sparingly and avoid generating very high
temperatures around these components.
Basic Component Tests
This section of the chapter briefl y explains how to
test basic electric and electronic components. Under-
standing these test procedures will help you later
when you study other, more specifi c tests.
Testing Connectors
A good connector has little or no resistance
across its terminals. A bad connector has resistance
that decreases current through the connector. This
reduced current can upset or stop the operation of
the circuit that contains the connector.
A test light can be used to check for power on
both sides of a connector. See Figure 22-30. This test
might be used when a circuit is completely dead,
indicating that power is not reaching a component
or section of a circuit. First, check for power going
into the connector. See Figure 22-31A. Then check
for power on the other side of the connector. Make
sure you check the same wire or terminal. Unless
you are testing a weather-pack connector, you can
touch the test probe on the terminals through the
outside of the connector. If the test light does not
glow on both sides of the connector, you have found
a high resistance or poor electrical connection.
Figure 22-22. Making ammeter readings on a digital multimeter.
A—Turn the function knob to A for amps. B—Plug the test leads
into the correct sockets for ammeter use. C—Notice the prefi x in
the units display. What does this ammeter read?
Figure 22-23. The bar graph on a digital-analog multimeter
allows you to see fl uctuating values easily. A—The analog bar
graph shows almost zero resistance. B—The bar has moved
all the way to the right to show a maximum resistance reading.
This can happen very rapidly and in quick succession, showing
rapid fl uctuations clearly.
C
B
A
A
B