Wiring and Circuit Protection (18.01)
Electric Distribution/E lectronic Control (18.00)
18-1-4 Workshop Manual May 2007
How to Read the Circuits
Below is a simple guide to what symbols mean on the circuit
diagrams. For some of the symbols there are descriptions as
to how they function.
Wires
Wires vary in size to allow diffe rent current to be carried. For
example a wire with a diamet er of 0.50mm (This is the
diameter of all the internal copper strands together) will
carry 11A (dependant on ambient temperature) whilst a wire
with a diameter of 2.00mm will carry 25A.
Twisted Wires
The ‘figure of 8’ shown on circuits as below denotes a
twisted wire and shows the wires that are twisted together.
A wire generates a certain amount of ‘electrical noise’ when
a current is passed through it. By twisting the 2 wires
together the ‘electrical noise’ is cancelled out on each wire
by the opposing wire. This is used more on sensors and
audio speakers.
Screened and Twisted Screen Wires
The signals through a wire can be affected by externally
generated electrical noise. To reduce the external
interference the wires are placed inside a conductive sleeve.
One end of the conductive sleeve is always open whilst the
other end can be terminated to a ground, to a component,
or left open.
Boot Fusebox
Fuse/
RelayRatingFunction
F1 5A Spare
F2 20A Spare
F3 30A Heated rear window
F4 20A Spare
F5 30A Spare
F6 20A Spare
F7 5A Battery disconnect switch (BDS) power
F8 20A Spare
F9 20A Tracker
F10 30A Spare
F11 20A Spare
F12 20A Spare
F13 10A Spare
F14 5A Rear parking assistance module (optional)
F15 5A Spare
F16 30A Spare
F17 5A Spare
F18 30A Audio amplifier
F19 5A Spare
F20 10A Canister vent
F21 30A Spare
F22 20A Exhaust by-pass and vacuum pump
Wire numbers have been deleted from the original
engineering circuits. This al lows the type size to be
increased for improved legibil ity of the service circuits.
173 WR 2.0
Wire No.
Colour
Size
908 GU MAPM 05
Wire No.
Colour
MAP (Defines twisted pair)
Size
Wiring and Circuit Protection (18.01)
Electric Distribution/E lectronic Control (18.00)
18-1-8 Workshop Manual May 2007
Relays
Another significant component in the circuits is a relay, this
is in simple terms a switch that operates on the principal of
electromagnetism. Below is the circuit symbol for a typical
relay. The relay shown below is a normally open relay in its
inoperative state i.e The arm is in the open position.
Relays can have either 4 or 5 terminals on the base. The
circuit of the relay is shown on the base or the side of the
housing. There are 2 types of numbering convention for the
relay terminals, both of which are shown below.
Below is a circuit diagram to show the function and
operation of a relay in a simple circuit.
The current from a battery for example flows through the
wires to the high power normally open switch (The arm
between pins 30 & 87A) and the low power coil (The box
between pins 85 & 86). As you can see in the example above
the lamp is in not illuminated, because the switch is open.
For the relay to operate there needs to be current flow
through the low power coil i.e Current in to the coil then
through to an earth. The current passes through the relay coil
and creates a magnetic field, this magnetic field is strong
enough to ‘grab’ the high power normally open switch.
The magnetic field pulls the switch from it’s normally open
contact to a normally closed contact. The normally closed
contact has a path to an earth, in this case it goes through a
lamp. The high power current then flows through the high power
normally open switch through the lamp and then to an earth.
This can be seen more clearly in the diagram below.Lamp
Illuminates
Busbars
A busbar is where a electrical
supply is fed into a conductive
bar, wire or pcb track and various modules or components
‘tap’ into this busbar to draw their required power. The
Central Electronic Module has 4 of these busbars internally,
each of which is supplied from an external power supply,
that supply can be a battery feed, ignition feed or a switched
supply.
The symbol shown below is the symbol used on the circuits
for a busbar, the number inside the box refers to the busbar
number in the Central Electronic Module.
Fuses
A fuse is a device used to protect a module or component
from excessive electrical current which can cause damage or
destroy that module or component. In practice the fuse is
placed in between the power source and the module or
component that is being protected.
The size or ‘Rating’ of the fuse in amps is calculated
according to the power requirements of the module or
component it is protecting with other factors being taken
into consideration. If the rating has been calculated correctly
then the fuse will ‘blow’ when excessive current passes
through it before any harm or permanent damage occurs to
the module or component it is protecting.
