SECTION 4 - 830P - TROUBLESHOOTING AND SCHEMATICS
4-2 – JLG Lift – 3121741
applied to a solenoid when it is only operational while a
switch, far from the solenoid and meter, is held down.
Polarity
Finding a negative voltage or current reading when
expecting a positive reading frequently means the leads
are reversed. Check what reading is expected, the location
of the signal and that the leads are connected to the
device under test correctly. Also check that the lead on the
"COM" port goes to the ground or negative side of the sig-
nal and the lead on the other port goes to the positive
side of the signal.
Scale
M = Mega = 1,000,000 * (Displayed Number)
k = kilo = 1,000 * (Displayed Number)
m = milli = (Displayed Number) / 1,000
μ = micro = (Displayed Number) / 1,000,000
Example: 1.2 kΩ = 1200 Ω
Example: 50 mA = 0.05 A
Continuity Measurement Over Long Distances
When trying to determine continuity of a harness or wire,
longer than the reach of standard instrument leads, is pos-
sible to perform the check without excessively long leads.
Using the other wires in the harness one can determine
the condition of a particular wire in the harness.
Requirements:
• Harness with at least three separate wires including
the wire under test.
• These wires must be able to be isolated from other
wires, etc.
• Jumper or method to connect contacts on one side of
harness.
• Meter that can measure resistance or continuity.
Procedure
Test multimeter leads resistance. Subtract this value from
the measured resistance of the wires to get a more accu-
rate measurement.
Consult the circuit schematic to determine which wires to
use in addition to wire under test, here called wire #1 and
wire #2, and how to isolate these wires. These wires should
appear in the same connectors as the wire under test or
are within reach of the jumper.
1.Disconnect all connections associated with the wire
under test and the two additional wires. If har-
ness is not completely isolated disconnect bat-
tery terminals also, as a precaution.
2.Measure continuity between all three wires, the wire
under test, wire #1 and wire #2. These should be
open. If not, repair the shorted wires or replace
the harness.
3.On one side, jumper from contact of wire #1 and wire
#2.
4.Measure continuity between wire #1 and wire #2. If
there is continuity, both wires are good and can
be used for this test. If there is not continuity,
either wire could be bad. Check connections and
measurement setup. Redo measurement. If still
no continuity, repair wires or consult schematic
for other wires to use for test.
5.Jumper from wire under test to wire #1.
6.Measure continuity. If there is continuity, the wire
under test is good. Resistance of a wire increases
as the length increases and as the diameter
decreases.
One can find the continuity of two wires, here #1 and #2,
at once by following steps 1 through 4. If there is a prob-
lem the third wire is used to troubleshoot the other wires.
To find the problem, start at step 1 and use the entire pro-
cedure.
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