Pontiac Fiero 1988 Service Manual page 937

T R O U B L E S H O O T I N G T O O L S
Electrical troubleshooting requires the use
of common electrical test equipment.
TEST LIGHT/VOLTMETER
Use a test light to check for voltage. A Test
Light (BT-7905 or equivalent) is made up of a
12-Volt light bulb with a pair of leads attached.
After grounding one lead, touch the other lead
to various points along the circuit where volt-
age should be present. When the bulb goes on,
there is voltage at the point being tested.
A voltmeter can be used instead of a test
light. While a test light shows whether or not
voltage is present, a voltmeter indicates how
much voltage is present.
An increasing number of circuits include
solid state control modules. One example is the
Electronic Control Module (ECM) used with
Computer Command Control and Electronic
Fuel Injection. Voltages in these circuits
should be tested only with a 10-megohm or
higher impedance digital voltmeter or multi-
meter (J-29125 or equivalent). Never use a test
light on circuits that contain solid state compo-
nents, since damage to these components may
result.
When testing for voltage or continuity at a
connection, you do not have to separate the
two halves of the connector. Unless you are
testing a "weather-pack" connector, you
should probe the connector from the back.
Always check both sides of the connector. An
accumulation of dirt and corrosion between
contact surfaces is sometimes a cause of elec-
trical problems.
CONNECTOR TEST ADAPTERS
A connector Adapter Kit is available
(J35616) for making tests and measurements at
separated connectors. This kit contains an
assortment of probes which mate with many of
the types of connectors you will see. Avoid
using paper clips and other substitutes since
they can damage terminals and cause incorrect
measurements.
SELF-POWERED TEST LIGHT
Use a self-powered test light (J-21008 or
equivalent) to check for continuity. This tool is
made up of a light bulb, battery, and two leads.
If the leads are touched together, the bulb will
go on.
A self-powered test light is used only on an
unpowered circuit. First disconnect the car s
Battery, or remove the fuse which feeds the cir-
cuit you Ye working on. Select two specific
points along the circuit through which there
should be continuity. Connect one lead of the
self-powered test light to each point. If there is
continuity, the test light s circuit will be com-
pleted and the bulb will go on.
Never use a self-powered test light on cir-
cuits that contain solid state components,
since damage to these components may result.
Self-Powered Test Light
OHMMETER
An ohmmeter can be used instead of a self-
powered test light. The ohmmeter shows how
much resistance there is between two points
along a circuit. Low resistance means good
continuity.
Circuits which include any solid state con-
trol modules, such as the Electronic Control
Module (ECM), should be tested only with a 10-
megohm or higher impedance digital multi-
meter (J-29125 or equivalent).
When measuring resistance with a digital
multimeter, the vehicle Battery should be dis-
connected. This will prevent incorrect read-
ings. Digital meters apply such a small voltage
to measure resistance that the presence of
voltages can upset a resistance reading.
Diodes and solid state components in a cir-
cuit can cause an ohmmeter to give a false
reading. To find out if a component is affecting
a measurement, take a reading once, reverse
the leads and take a second reading. If the
readings differ, the solid state component is
affecting the measurement.