Chapter 22 Basic Electrical Tests 359
Freeze spray can be used to fi nd intermittent prob-
lems in electronic components. Electronic compo-
nents are very sensitive to temperature. When you
spray the freeze solution on a component, the com-
ponent’s temperature lowers instantly. This may
cause a change in the component’s output, helping
you fi nd some internal problems.
Green Tech
Fluorescent Shop Lights
To keep your shop energy effi cient, one step you
can take is to replace any high-power lights with fl uo-
rescent lights. There are varying levels of effi ciency
in fl uorescent lights as well. The T system designates
the tube diameter for fl uorescent lamps. Older fl uo-
rescent lights may be T12 lights. To be more effi cient,
these should be replaced with T8 lights. The lights
with smaller diameters will give off more light and use
less power.
Summary
❚ Most circuit problems are caused by something
very simple, such as a broken wire or loose termi-
nal connection. However, when this basic trouble
is in a complex circuit, it can be very diffi cult to
locate and repair. Correct techniques must be used
to fi nd electrical problems in a modern vehicle.
❚ Use a systematic approach to diagnose electri-
cal trouble. First verify a problem and analyze
the symptoms. Then narrow down the possible
causes of the problem. Perform the proper tests
to fi nd the exact trouble. After making the repair,
recheck to be sure the problem has been corrected
before releasing the vehicle to the customer.
❚ If only one component does not work, start your
tests at that component. If several components in
the same circuit are not working, start your tests
at the power source to the circuit.
❚ Common circuit problems include an open cir-
cuit, high circuit resistance, short circuit, and
intermittent circuit problems.
❚ Jumper wires, test lights, inductive circuit tracers,
and multimeters are important testing devices and
can be used to fi nd most types of circuit trouble.
Figure 22-39. Use this circuit illustration to answer review questions 21 through 25.
A
B
C
D
Switch
Open Closed
Fuse
Bulb Dim
(Disconnect Bulb
While Testing)
~V
OFF
V
Ω
mA
mA
A
~
10 V
+
–
~V
OFF
V
Ω
mA
mA
A
~
2 V
~V
OFF
V
Ω
mA
mA
A
~
0.0
Ω