Chevrolet TrailBlazer, Service Manual, Page: 340 / 677

reason, the flow of current through the circuit is interrupted, the component fed by that
circuit will cease to function properly.
Perhaps the easiest way to visualize a circuit is to think of connecting a light bulb (with two
wires attached to it) to the battery-one wire attached to the negative (
–) terminal of the
battery and the other wire to the positive (+) terminal. With the two wires touching the
battery terminals, the circuit would be complete and the light bulb would illuminate.
Electricity would follow a path from the battery to the bulb and back to the battery. It's easy
to see that with longer wires on our light bulb, it could be mounted anywhere. Further, one
wire could be fitted with a switch so that the light could be turned on and off.
This example illustrates a simple circuit. When the switch is
closed, power from the positive (+) battery terminal flows
through the fuse and the switch, and then to the light bulb.
The light illuminates and the circuit is completed through the
ground wire back to the negative (
–) battery terminal. In
reality, the two ground points shown in the illustration are
attached to the metal frame of the vehicle, which completes
the circuit back to the battery
The normal automotive circuit differs from this simple example in two ways. First, instead
of having a return wire from the bulb to the battery, the current travels through the frame of
the vehicle. Since the negative (
–) battery cable is attached to the frame (made of
electrically conductive metal), the frame of the vehicle can serve as a ground wire to
complete the circuit. Secondly, most automotive circuits contain multiple components