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WIRING
AND LIGHTING
Tool and Material Checklist:
- Test light
- Fuse p
- Service manual
- Cloth or paper
- Penetrating oil
- Wire brush or abrasive
- Long-nose pliers paper
- T-square or right angle
- Metal clips or nylon wire
- Screwdriver ties
- Black electrical tape
- Fuses
Many important jobs related to your cars electrical system can be done easily and safely, if
proper care is observed. With the exception of the
headlights, most bulbs can be changed with little
effort. The circuits that carry electrical current
from the battery to the individual components are
illustrated in detail in your car's service manual.
Refer to these diagrams for specifics or to trouble-
shoot problems that cannot be corrected with the
general information given in this project.
OPEN CIRCUITS
An open circuit is simply a switch that is off, a
break in a wire, or a burned-out bulb. Open circuits are usually caused by breaks
in the wiring,
faulty connections, or mechanical failure in a
switch or component. They cause components to
fail, but they do not cause fuses to "blow." Use a
test light to pinpoint an open circuit. For example,
if the wipers fail to operate, proceed as follows:
1. Turn on the switch to the wiper accessory.
2. Attach the test light clamp to a good ground
(some bare metal part of the car body, chassis, or
engine). To make sure the ground is good, touch
the probe to a known hot source such as the battery or cigarette lighter socket.
3. After locating the fuse, touch the probe to
one end of the fuse holder, then to the other. If it
lights in both cases, the fuse is good. If it lights at
one end only, replace the fuse.
4. If the fuse is not bad, touch the probe to the
wires at the wiper switch. If the test light comes
on, the wire between the fuse and switch is
unbroken.
5. Check the terminal and the wire that extends
from the switch to the wiper. If there is current
coming out of the switch to the wiper itself, the
switch is good.
6. Check the mounting of the wiper by attaching
the clamp of the probe to a hot wire and touching
the probe to the housing or case of the wiper. If
the ground is poor or nonexistent, the light will not
work. If the light goes on, the ground is good and
the problem is in the wiper motor itself. Check for
current at the motor in the same manner to con-
firm the diagnosis.
FUSES
Fuses act as safety valves for electricity by pre-
venting damage caused by short circuits and over-
loads. If a short or overload causes the circuit's
current drain to exceed the amp rating of the fuse,
the fuse "blows" and switches off the current to
that circuit. All fuses are contained in the fuse
block, which is located on the inside of the fire
wall, usually on the driver's side. It is labeled with
the name of the circuit (s) each fuse protects and,
in most cases, the amp rating of the correct fuse.
When a blown fuse is detected, either visually or
by test light, replace it with a new one of the same
amp rating. If this new fuse blows, check for a
short or a temporary overload. For example, If the
wipers are turned on while the blades are frozen to
the glass, a temporary overload can result. If you
don't have a fuse puller to remove blown fuses, use
half of a hinged clothespin. Be careful-glass
fuses can break easily.
SHORT CIRCUITS
A short circuit occurs when electricity finds a
short cut" from positive to negative; it is the result
of a bare spot on the wire contacting part of the
metal car body. The windings in electric motors
can also short. Short circuits are hazardous be-
cause they create sparks, burned wires, and blown
fuses. They are more difficult to locate with a test
light than open circuits.
1. Disconnect the suspected circuit at all points
where it is joined by connectors (you'll need the
wiring diagram for this).
2. Attach the clamp of the tester to the hot side
of that circuit's fuse and touch the probe to the
other side of the blown fuse. If the light goes on,
the short is between the fuse and the first disconnected connector.
3. If the light doesn't go on, connect the first
connector and touch the probe to the fuse holders
again. If the light goes on, the short is between the
first and second connector.
4. If the light again does not go on, repeat the
process until the section of the wire with the short
is isolated.
HEADLIGHTS
Two-light systems have one headlight on each
side, each of which has a high-beam and a low-
beam filament. Four-light systems have two lights
on each side; two of them should be lit for low
beam and all four for high beam. To replace a
burned-out headlight:
1. Remove the trim ring or headlight bezel.
2. Remove the three screws (four on rectangular
lights) from the retaining ring. If difficult to re-
move, apply penetrating oil.
NOTE: Do not disturb the two adjusting screws
(the screws with springs under them). This will
throw off the headlight adjustment.
3. With the retaining ring off, pull the headlight
out.
4. Remove the plug-in socket at the back of the
light. Test the headlight for current to make sure
the beam was the problem.
5. Install the plug on the new headlight, making
sure that the prongs on the light and those on the
socket are properly aligned.
6. Install the retaining ring, making sure that the
light is properly aligned before tightening the retaining ring screws. The headlight has locating
lugs around the back of the glass that fit in the
notches of the adjusting house.
7. Replace the trim ring or decorative panel.
ADJUSTING HEADLIGHTS
1. Consult your service manual for the correct
tire pressure and how much gasoline should be in
the tank, both of which affect the height and angle
of the headlight beam.
2. Use a T-square or right angle to draw a perpendicular line through the center of a large board
or one of your garage doors.
3. Draw a horizontal line at the same height
from the base of the board or door as the center of
the headlights are from the ground. Draw two lines
if your car has headlights one over the other one
each side.
4. Measure the distance from each headlight
center to the center of the car.
5. On the diagram, measure and mark this distance along the horizontal from the center
perpendicular line.
6. Draw vertical lines through these marks. If
your car has two side-by-side headlights on each
side, you will need a total of four vertical lines.
7. Position the front of the car exactly 25' from
and parallel to the diagram, with the car's center
pointed exactly at the vertical centerline on the
diagram.
8. After dark, switch the headlights on high
beam and cover all but one with cloth or paper.
9. Make the adjustment by using the horizontal
and vertical adjustment screws. The bright center
(or hot spot) is 2" below the intersection of the
horizontal and vertical centerlines on the diagram,
corresponding to that headlight.
10. Repeat for all headlights, then switch to low
beam.
11. On four-headlight cars, adjust the low-beam
headlights so that the hot spot is 2" to the right of
the vertical headlight centerlines, with the top of
the hot spot just touching the horizontal line. On
two-headlight cars, this should be automatically
corrected if the high beam was adjusted properly.
EXTERIOR BULBS
Gain access to exterior bulbs by removing the
screws that retain the lens, then the lens itself.
Many exterior bulbs must be removed from the
back of the light housing, usually from the inside
of the trunk or under the fender. With rear-access
housing, remove the socket itself by turning it 1/4
turn counterclockwise and pulling it out of the
housing. The rest of the bulb removal procedure is
the same for either front or rear access.
1. Gently grasp the globe and push it down into
the socket, turning it counterclockwise 1/4 turn until it stops. If the bulb will not turn, use penetrating
oil.
2. Lift out the bulb. If it is broken, you will need
long-nose pliers to grasp the base, push, turn, and
pull in out.
3. Reverse the procedure for installation. If the
bulb will not turn after pushing it down, take it out,
turn it 180°, and reinsert it.
4. With the rear-access light, install the socket in
the housing and test the light. There is no need to
do this with the front-access light because the
socket is fixed to the ground.
5. If the bulb does not light and it is definitely
good, wiggle the bulb in its socket. If it lights,
clean off any corrosion at the base or side of the
socket with a small wire brush or abrasive paper.
6. If the contact at the bottom of the socket is
corroded beyond correction, a replacement con-
tact with attached wire can be purchased. This is
called a pigtail assembly and is available with one
or two contacts.
7. If corrosion is not the problem, check the
grounding of the socket.
8. If properly grounded, check for an open circuit in the hot wire.
FLASHERS
Most cars have two small can-shaped or box-
shaped units that make a tick-tick sound when the
turn signals or hazard warning lights are activated.
These flashers are usually mounted under the
dash on the driver's side; they can also be mount-
ed to the fuse block or taped to a wiring harness. A
test light can be used to determine which flasher is
used for the turn signals and which is used for the
hazard warning lights. An easier way is to turn on
both the directionals and the hazards; this will activate both flasher units. By removing one of the
flashers, you will disable one of the circuits and
thus find out which flasher operates which system.
If your turn signals fail to operate and the fuse is
good, the flasher has probably failed. Occasionally, the flasher will not flash as fast as it once did, or
it will flash faster; this is also cause for replacement. (If it flashes too fast or too slowly, check for
a burned-out bulb first.) A flasher features two or
three prongs that plug into a socket, Just pull the
prongs out of the socket and replace with a new
flasher. Flashers are designed to operate a specific
number of bulbs of a specific candlepower
(brightness), If the candlepower of the turn signal
bulbs is changed, or if additional bulbs are used (if
you hook up a trailer, for instance), a heavy-duty
flasher must be used. This will fit your socket
without modifications.
ACCESSORIES
When adding accessories (radios, driving lights,
clocks, etc.), there are-several procedures to follow
to ensure a safe and trouble-free installation.
1. Be sure you use wire of the proper gauge.
The installation instructions received with the accessory will specify this, as well as the proper amp
rating of the fuse. While some people use knives or
razor blades to strip insulated wires, the use of
wire stripping pliers is recommended. This tool
strips any standard gauge wire quickly and accurately. The tip of the jaws is a wire cutter, and
immediately behind the cutter the jaws are hollowed
out for crimping.
2. Be sure the new circuit is fused. Some fuse
panels already have a fuse labeled "additional accessories"; use this if possible. Others have
additional holders where circuits can be added. If one
of these is not available, an in-line fuse and fuse
holder can be purchased. Check your fuse panel
for a spade terminal that is vacant, and use the test
light to see if it is hot. For accessories that you
want controlled by the key, do the test with the key
in both the on and off positions. Attach the in-line
fuse to this spade terminal and position the fuse
holder so that it is accessible. Attach your wire
from the other end of the fuse holder to your accessory (or to the switch, if one is used).
3. Be sure all connections are mechanically and
electrically sound. Solderless insulated terminals
and connectors are commonly used in most auto-
motive applications.
4. Be sure that the wiring is routed in a safe and
protected manner. Do not permit it to come in con-
tact with moving parts. Either tape it to an existing
wire or purchase metal clips or nylon wire ties to
fasten it to a solid surface. If you must drill a hole
for the wire to pass through, protect the wire with
a rubber grommet in the hole, or make several
wraps of tape around the wire where it passes
through the hole.
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