you purchase a new electrical component(s), install it, and then find that the system still
does not work properly, you will probably be unable to return the unit for a refund.
Consider any test results carefully before replacing a component that teats only
slightly out of specification, especially resistance. A number of variables can affect test
results dramatically. These include: the testing meter’s internal circuitry, ambient
temperature and conditions under which the machine has been operated. All
instructions and specifications have been for accuracy: however. Successful test
results depend to a great degree upon individual accuracy.
Test Equipment
A test light can be constructed from a 12-volt light bulb with a pair of test leads
carefully soldered to the bulb. To check for battery voltage in a circuit, attach one lead
to ground and the other lead to various points along the circuit. The bulb lights when
battery voltage is present.
A voltmeter is used in the same manner as the test light to find out if battery
voltage is present in any given circuit. The voltmeter, unlike the test light, also indicates
how much voltage is present at each test point. When using a voltmeter, attach the
positive lead to the component or wire to be checked and the negative lead to a good
ground.
Ammeter
An ammeter measures the flow of current (amps) in a circuit when connected in
series in a circuit, the ammeter determines if current is flowing through the circuit and if
that current flow is excessive because of a short in the circuit. Current flow is often
referred to as current draw. Comparing actual current draw in the circuit or component
to the manufacturer’s specified current draw provides useful diagnostic information.
Self-powered test light
A self-powered test light can be constructed from a 12-volt light bulb, a pair of test
leads and a 12-volt battery. When the test leads are touched together, the light bulb
should go on.
Use a self-powered test light as follows:
1. Touch the test leads together to make sure the light bulb goes on. If not, correct the
problem before using it in a test procedure.
2. Select two points within the circuit where there should be continuity.
3. Attach one lead of the self-powered test light to each point.
4. If there is continuity, the self-powered test light bulb will come on.
5. If there is on continuity, the self-powered test light bulb will not come on, indicating
an open circuit.
Ohmmeter
An ohmmeter measures the resistance (in ohms) to current flow in a circuit or
component. Like the self-powered test light, an ohmmeter contains its own power
source and should not be connected to a live circuit.
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