Workshop Manual

TROUBLESHOOTING INSTRUCTION
WS-11
TROUBLESHOOTING EQUIPMENTS
Voltmeter And Test Lamp
Use a test lamp or a voltmeter on circuits without solid-state units,
use a test lamp to check for voltage. A test lamp is made up of 12-
volt bulb with a pair of leads attached. After grounding one lead to
various points along the circuit where voltage should be present.
When the bulb goes on, there is voltage at the point being tested.
CAUTION:
A number of circuits include solid-state modules such as
Electronic Control Unit (ECU) used with computer command
control injection. Voltage in these circuits should be tested
only with a 10-megohm or higher impedance digital voltmeter.
Never use a test lamp on circuits that contain solid-state units.
Damage to the units may result.
A voltmeter can be used in place of a test lamp. While a test lamp
shows whether the voltage is present or not, a voltmeter indicates
how much voltage there is.
Self-Powered Test Lamp And Ohmmeter
Use a self-powered test lamp or a ohmmeter to check for continuity.
Self-powered test lamp is made of a bulb, battery and two leads and
is used only on an unpowered circuit. If the leads are touched
together, the lamp will go on. Prior to checking the points, first
disconnect the battery ground cable or remove the fuse which feeds
the circuit you are working on.
CAUTION:
Never use a self-powered test lamp on circuits that contain
solidstate units. Damage to these units may result.
An ohmmeter can be used in place of a self-powered test lamp.
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 devices should be tested only
with a 10-megohm or higher impedance digital multimeter. When
measuring resistance with a digital multimeter, battery negative
terminal should be disconnected. Otherwise, there may incorrect
readings. Diodes and solid-state devices in a circuit can make an
ohmmeter give a false reading. To find out if a component is
affecting a measurement, take one reading, reverse the leads and
take a second reading. If the readings differ, the solid-state device
is affecting the measurement.