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wire. Main power distribution circuits and larger accessories usually use 10 and 12
gauge wire. Battery cables are usually 4 or 6 gauge, although 1 and 2 gauge
wires are occasionally used. Wire length must also be considered when making
repairs to a circuit. As conductor length increases, so does resistance. An 18
gauge wire, for example, can carry a 10 amp load for 10 feet without excessive
voltage drop; however if a 15 foot wire is required for the same 10 amp load, it
must be a 16 gauge wire.
WIRING DIAGRAMS
An electrical schematic shows the electrical current paths when a circuit is
operating properly. It is essential to understand how a circuit works before trying
to figure out why it doesn't. Schematics break the entire electrical system down
into individual circuits and show only one particular circuit. In a schematic, no
attempt is made to represent wiring and components as they physically appear on
the vehicle; switches and other components are shown as simply as possible.
Face views of harness connectors show the cavity or terminal locations in all
multi-pin connectors to help locate test points.
If you need to backprobe a connector while it is on the component, the order of
the terminals must be mentally reversed. The wire color code can help in this
situation, as well as a keyway, lock tab or other reference mark.
WIRING REPAIR
Soldering is a quick, efficient method of joining metals permanently. Everyone
who has the occasion to make wiring repairs should know how to solder. Electrical
connections that are soldered are far less likely to come apart and will conduct
electricity much better than connections that are only "pigtailed'' together. The
most popular (and preferred) method of soldering is with an electric soldering gun
or iron. Soldering irons are available in many sizes and wattage ratings. Irons
with higher wattage ratings deliver higher temperatures and recover lost heat
faster. A small soldering iron rated for no more than 50 watts is recommended,
especially on electrical systems where excess heat can damage the components
being soldered.
There are three ingredients necessary for successful soldering; proper flux, good
solder and sufficient heat. A soldering flux is necessary to clean the metal of
tarnish, prepare it for soldering and to enable the solder to spread into tiny
crevices. When soldering, always use a rosin flux or rosin core solder which is
non-corrosive and will not attract moisture once the job is finished. Other types of
flux (acid core) will leave a residue that will attract moisture and cause the wires
to corrode. Tin is a unique metal with a low melting point. In a molten state, it
dissolves and alloys easily with many metals. Solder is often made by mixing tin
with lead. The most common proportions are 40/60, 50/50 and 60/40, with the
percentage of tin listed first. Low priced solders usually contain less tin, making
them very difficult for a beginner to use because more heat is required to melt
the solder. A common solder is 40/60 which is well suited for all-around general
use, but 60/40 melts easier, has more tin for a better joint and is preferred for
electrical work.
Soldering Techniques
Successful soldering requires that the metals to be joined are heated to a
temperature that will melt the solder-usually 360-460°F (182-238°C). Contrary to
popular belief, the purpose of the soldering iron is not to melt the solder itself,
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