Ford Taurus, Руководство пользователя

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Open Circuit Testing
To use the self-powered test light to check for open circuits, first isolate the
circuit from the vehicle's 12 volt power source by disconnecting the battery or
wiring harness connector. Connect the test light ground clip to a good ground and
probe sections of the circuit sequentially with the test light. Start testing from
either end of the circuit. If the light is out, the open is between the probe and the
circuit ground. If the light is on, the open is between the probe and end of the
circuit toward the power source.
Short Circuit Testing
By isolating the circuit both from power and from ground, and using a self-
powered test light, you can check for shorts to ground in the circuit. Isolate the
circuit from power and ground. Connect the test light ground clip to a good
ground and probe any easy-to-reach test point in the circuit. If the light comes
on, there is a short somewhere in the circuit. To isolate the short, probe a test
point at either end of the isolated circuit (the light should be on). Leave the test
light probe connected and open connectors, switches, remove parts, etc.,
sequentially, until the light goes out. When the light goes out, the short is
between the last circuit component opened and the previous circuit opened.
The 1.5 volt battery in the test light does not provide much current.
Aweak battery may not provide enough power to illuminate the test light
evenwhen a complete circuit is made (especially if there are high
resistances inthe circuit). Always make sure that the test battery is
strong. To check thebattery, briefly touch the ground clip to the probe; if
the light glowsbrightly the battery is strong enough for testing. Never
use a self-poweredtest light to perform checks for opens or shorts when
power is applied to theelectrical system under test. The 12 volt vehicle
power will quickly burn outthe 1.5 volt light bulb in the test light.
Voltmeter
A voltmeter is used to measure voltage at any point in a circuit, or to measure
the voltage drop across any part of a circuit. It can also be used to check
continuity in a wire or circuit by indicating current flow from one end to the other.
Voltmeters usually have various scales on the meter dial and a selector switch to
allow the detection of different voltages. The voltmeter has a positive and a
negative lead. To avoid damage to the meter, always connect the negative lead to
the negative (-) side of circuit (to ground or nearest the ground side of the
circuit) and connect the positive lead to the positive (+) side of the circuit (to the
power source or nearest the power source). Note that the negative voltmeter lead
will always be black and that the positive voltmeter will always be some color
other than black (usually red). Depending on how the voltmeter is connected into
the circuit, it has several uses.
A voltmeter can be connected either in parallel or in series with a circuit, and has
a very high resistance to current flow. When connected in parallel, only a small
amount of current will flow through the voltmeter current path; the rest will flow
through the normal circuit current path and the circuit will work normally. When
the voltmeter is connected in series with a circuit, only a small amount of current
can flow through the circuit. The circuit will not work properly, but the voltmeter
reading will show if the circuit is complete or not.
Стр . 5 из 16 UNDERSTANDING AND TROUBLESHOOTING ELECTRICAL SYSTEMS
18.11.2005 http://www.chiltondiy.com/content/8687/8687_6_1.html