358 Section 3 Fundamentals of Electricity and Electronics
Tech Tip
Most transistors in complex circuits require the
expertise of a specialized circuit technician.
However, some power transistors in various
devices frequently fail and can be checked
and replaced in the fi eld.
Testing other Components
Methods for testing other electric and electronic
components are discussed in later chapters. How-
ever, most testing requires the techniques dis-
cussed in this chapter. Figure 22-38 shows how
an ohmmeter and voltmeter can be used to test
various components. If you use common sense,
your knowledge of component operation, and
recommended testing practices, you should have
little trouble finding problems.
Electrical Service Chemicals
Several chemicals can be helpful when you are
doing electrical tests and repairs. Electrical solvent
can be used to clean oil and grease from compo-
nents before soldering. It can also be used to remove
soldering fl ux from a component. Contact cleaner
is a chemical for cleaning deposits from contacts,
switches, and other components.
Figure 22-38. You must use common sense and the basic rules given in this chapter when making electrical measurements. By
thinking about the circuit and specifi c components, you should be able to use logical steps to fi nd circuit problems.
– +
Signal
processor
Ohmmeter
Ohmmeter
Disconnect
wires to check
continuity
Typical sensor
(input information)
Checking
for good
ground
ECM
ground
Ohmmeter
Voltage
drop
Electronic
control module
Typical
solenoid
(controlled
function)
Voltmeter
Disconnected
component
Check supply
voltage
R
battery
voltage
Voltmeter