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BASIC TESTS CONT.
removing wires from a threaded power terminal.
Separate the wiring harness at the plug, or worst case
scenario, cut the wires.
4. Disconnect wiring harness.
5. Attach your alligator clips to the probes, black on
black, red on red.
6. Connect RED alligator clip to one side of the
disconnected circuit.
7. Connect BLACK alligator clip to remaining side of
disconnected circuit.
8. Turn multimeters range selector to 10A DC
position, or 200mA position.
9. Read the meter display for your results. If the results
displayed are negative (-), then reverse RED and
BLACK test leads. See display for corrected results.
Resistance Test
This meter measures resistance from 0.1Ω to
20MΩ. Infinite resistance is shown with the “1”
figure on the left side of display. This meter can
measure resistance on anything called out in your
vehicles service manual. Testing light bulbs, ignition
coils/wires, engine sensors, and wires circuits, are
just some of the tests the Ohms function can do.
1. Turn circuit power off to get a resistance
measurement and avoid possible damage to the
meter or electrical circuit getting tested, turn off all
electrical power to the circuit.
2. Insert BLACK test lead into COM test lead jack.
3. Insert RED test lead into test lead jack.
4. Turn multimeters range selector to 200Ω range.
5. Touch RED and BLACK multimeter leads
together and view reading on display. Display
should read typically 0.2Ω to 1.5Ω. If display
reading was greater than 1.5Ω, check both ends of
test leads for bad connections. If bad connections
are found, replace test leads.
6. Connect RED and BLACK test leads across
component where you want to measure resistance.
When measuring resistance, polarity is not
important. The test leads just have to be connected
across the component.
7. Turn multimeters range selector to desired OHM
range. If the approximate resistance is unknown, start
at the largest OHM range and decrease to the
appropriate range as required. View reading on
display. Note range setting for correct units.
NOTE: 2KΩ = 2,000Ω; 2MΩ = 2,000,000Ω
For precise resistance measurements, subtract the
test lead resistance found from the display reading.
Do this for resistance measurements less than 10Ω.
Continuity Test
A quick way to check if you have an open or closed
circuit. The meter beeps when the circuit is closed
or shorted, so you don’t need the meters display in
view. A common automotive use is checking for
blown fuses, proper switch operation, and broken or
shorted wires.
1. Insert BLACK test lead into COM test lead jack.
2. Insert RED test lead into test lead jack.
3. Turn meters range selector to function.
4. Touch RED and BLACK test leads together to
test continuity. You should hear a tone to verify.
5. Connect RED and BLACK test leads across the
circuit where you want to check for continuity. If you
hear tone the circuit is closed or shorted. If there is
no tone the circuit is open.
Diode Test
Automotive alternators generates AC voltage, the
diode inside converts it to DC voltage allowing
current to flow in only one direction. When positive
voltage > 0.5V, is applied to the anode side of the
diode, the diode will turn on and allow current to flow.
If this same voltage is applied to the cathode side,
the diode would remain off and no current would flow.
When testing the diode both sides need to be
checked, anode-to-cathode, and cathode-to anode.
1. Insert BLACK test lead into COM test lead jack.
2. Insert RED test lead into test lead jack.
3. Turn the meters range selector to function.
4. Touch RED and BLACK test leads together to
test continuity. The display should show 0.00 and an
audible tone should be heard.
5. Disconnect one end of the diode from the circuit.
The diode must be totally isolated from circuit in
order to verify its function.
6. Add the alligator clips and connect RED clip to
one side of the diode.
7. Connect BLACK clip to the other end of the diode.
View results on the display, you should see one of
three things. A typical voltage drop of 0.7V, no
voltage drop at all, or the meter will display “1” on
the far left (overranging). Record the results.
8. Now switch the RED and BLACK clips and view
the results. If the display showed no voltage drop in
either directions, then the diode is shorted and needs
to be replaced. If the “1” appears in both directions,
then the diode is an open circuit and needs to be
replaced. If the display reads > 0.5V in one direction
and the “1” appears in the other direction then the
diode is good and functioning properly.
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