Test Lights - Ford Ranger Maintaince And Repair Manual

HOW TO USE THIS BOOK
pin connector) that is required for the particular application being tested. In cramped, hard−to−reach areas, it
is advisable to have insulated boots over the jumper wire terminals in order to prevent accidental grounding. It
is also advisable to include a standard automotive fuse in any jumper wire. This is commonly referred to as a
"fused jumper". By inserting an in−line fuse holder between a set of test leads, a fused jumper wire can be
used for bypassing open circuits. Use a 5 amp fuse to provide protection against voltage spikes.
Jumper wires are used primarily to locate open electrical circuits, on either the ground (−) side of the circuit or
on the power (+) side. If an electrical component fails to operate, connect the jumper wire between the
component and a good ground. If the component operates only with the jumper installed, the ground circuit is
open. If the ground circuit is good, but the component does not operate, the circuit between the power feed
and component may be open. By moving the jumper wire successively back from the component toward the
power source, you can isolate the area of the circuit where the open is located. When the component stops
functioning, or the power is cut off, the open is in the segment of wire between the jumper and the point
previously tested.
You can sometimes connect the jumper wire directly from the battery to the "hot" terminal of the component,
but first make sure the component uses 12 volts in operation. Some electrical components, such as fuel
injectors or sensors, are designed to operate on about 4 to 5 volts, and running 12 volts directly to these
components will cause damage.

TEST LIGHTS

A 12 volt test light is used to detect the presence of voltage in a circuit
The test light is used to check circuits and components while electrical current is flowing through them. It is
used for voltage and ground tests. To use a 12 volt test light, connect the ground clip to a good ground and
probe wherever necessary with the pick. The test light will illuminate when voltage is detected. This does not
necessarily mean that 12 volts (or any particular amount of voltage) is present; it only means that some
voltage is present. It is advisable before using the test light to touch its ground clip and probe across the
battery posts or terminals to make sure the light is operating properly.
WARNING
Do not use a test light to probe electronic ignition, spark plug or coil wires. Never use a pick−type test light to
probe wiring on computer controlled systems unless specifically instructed to do so. Any wire insulation that
is pierced by the test light probe should be taped and sealed with silicone after testing.
Like the jumper wire, the 12 volt test light is used to isolate opens in circuits. But, whereas the jumper wire is
used to bypass the open to operate the load, the 12 volt test light is used to locate the presence of voltage in a
JUMPER WIRES 657