1. Connect the positive meter test lead to the electrical source (where electricity is
coming from).
2. Connect the voltmeter negative test lead to the electrical load (where the electricity is
going).
3. If necessary, activate the component(s) in the circuit. For example. If checking the
voltage in the starter circuit, it would be necessary to push the starter button.
4. Read the voltage drop (difference in voltage between the source and destination) on
the voltmeter. Note the following:
a. The voltmeter should indicate 0 volts. If there is a drop of 0.5 volts or more. There
is a problem within the circuit. A voltage drop reading of 12 volts indicates an open
in the circuit.
b. A voltage drop of 1 or more volts indicates that a circuit has excessive resistance.
c. For example, consider a starting problem where the battery is fully charged but
the starter motor turns over slowly. Voltage drop would be the difference in the
voltage at the batter (source) and the voltage at the starter (destination) as the
engine is being started (current is flowing through the batter cables). A corroded
battery cable would cause a high voltage drop (high resistance) and slow engine
cranking.
d. Common sources of voltage drop are loose or contaminated connectors and poor
ground connections.
Peak voltage test
Peak voltage tests check the voltage output of the ignition coil and ignition pulse
generator at normal cranking speed. These tests make it possible to identify ignition
system problems quickly and accurately.
Peak voltage tests require a peak voltage adapter or tester. See Chapter Ten,
Ignition System Testing.
Continuity Test
A continuity test is used to determine the integrity of a circuit, wire or component. A
circuit has continuity if it forms a complete circuit, that is, if there are no opens in either
the electrical wires or components within the circuit. A circuit with an open. On the
other hand, has no continuity.
This type of test can be performed with a self-powered test light or an ohmmeter.
An ohmmeter gives the best results. If using an analog ohmmeter, calibrate the meter
by touching the leads together and turning the calibration knob until the meter reads
zero.
1. Disconnect the negative battery cable.
2. Attach one test lead (test light or ohmmeter) to one end of the part of the circuit to
be tested.
3. Attach the other test lead to the other end of the part or the circuit to be tested.
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