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Throughout this instruction manual and when looking at the Painless harness you
will see the word GROUND, maybe you’ve seen the ground symbol on wire diagrams?
What exactly is a ground and why do you need it?
You’ve probably noticed the large cable coming
from the negative side of your battery going down to the
sub frame or to the engine. This cable allows voltage to
get back to the battery through the metal of the sub
frame and all the other metal pieces bolted to the frame.
It is also important to have ground cables going from the
sub frame to the engine and from the sub frame to the
body. Painless offers part #
40140
, seen in the photo
,
to
supply proper grounds back to the battery.
A ground is simply the common path voltage takes back to the battery. A ground,
or chassis ground as it is often called, is any bare metal surface found on the vehicle
which is in turn connected back to the frame/negative side of the battery through
mounting points and ground straps. They are needed in order for the voltage current to
have some place to go.
There are two ways components are grounded in vehicles: through mounting and
through wire connection.
Some grounds are supplied though the mounting of the metal housings in which bulbs
are installed, like turn signal or tail light housings. Components with plastic housings or
non conductive housings, like headlights which are glass, get their grounds through
wires from the chassis harness.
To help avoid grounding problems, all the ground wires in the Painless harness
are connected together through a series of splices. All of these splices connect to a
large 10 gauge wire found in the COMPONENT OUTPUT HARNESS, see the
Ground
Schematic
on page14.
On light housings that ground through the mounting and for the harness ground
wire connection point make sure that all mounting points are clean by removing all dirt,
corrosion, or paint. This is especially important for cars that have recently been painted
as paint build up will cause grounding issues. 80 grit or courser sandpaper should be all
that’s needed to properly clean grounding points.
Why are clean grounds important
?
As an example we will use a front turn signal that also functions as a park light.
Follow the red line from right to left in the diagrams on the next page. This red line
indicates the path electrical current takes when everything is properly grounded and as
represented in the second diagram, when the ground is bad; notice which bulbs
illuminate when good and bad grounds are present.
In our park light example with a good ground source, current travels from the
headlight switch to the park light bulb. Since the bulb is properly grounded, current
