Series 1000 and 1500
81
39.17.As a point of illustration, a short length of 12 or
14 gauge stranded wire can be stripped at the
ends to facilitate an Ohm reading.
See Figure
39.17.
39.18.For comparison, strip away insulation at the mid-
dle of the wire, and snip strands until only a few
remain. Repeat the Ohm reading. There will
not be a substantial change.
See Figure 39.18.
• While the actual resistance did not change, the
ability of the whittled-down length of wire to carry
current is vastly reduced.
• Similar effects occur when a terminal is not firmly
crimped, a connection is loose, insulated by
paint or corrosion, or the wire is chafed, cut, or
corroded.
Figure 39.17
Undamaged
wire
Figure 39.18
Stripped and
partially severed
wire
39.19.A more effective way to identify this reduced cur-
rent carrying capacity is to look for “voltage
drop”.
39.20.Voltage drop tests are useful on both the positive
or the negative side of the system. We will con
-
centrate on the negative side to begin with. See
Figure 39.20.
• Ultimately, any negative current should find its
way back to the negative post of the battery.
• To check ground-side voltage drop: set-up a
multi meter to measure 12V DC.
• Make a good electrical connection between the
black (-) probe and the negative post on the bat-
tery.
• Make a good electrical connection between the
red (+) probe and the suspect point of ground.
• Power-up the circuit in question.
• The voltage that shows-up on the meter is the
power that is not following the intended path
back to the negative battery post.
• Voltage drop on a good circuit should be less
than 0.1 volts. A voltage drop reading on the
meter of greater than 0.2 volts indicates a fairly
substantial problem that demands attention.
Figure 39.20
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