
1 General information,precautions and battery
disconnection
General information
The engine electrical system consists
mainly of the charging and starting systems.
Because of their engine-related functions,
these components are covered separately
from the body electrical devices such as the
lights, instruments, etc (which are covered in
Chapter 12). Information on the ignition
system is covered in Part B of this Chapter.
The electrical system is of the 12-volt
negative earth type. The battery is of the low maintenance or
“maintenance-free” (sealed for life) type and is
charged by the alternator, which is belt-driven
from the crankshaft pulley. The starter motor is of the pre-engaged
type incorporating an integral solenoid. On
starting, the solenoid moves the drive pinion
into engagement with the flywheel ring gear
before the starter motor is energised. Once
the engine has started, a one-way clutch
prevents the motor armature being driven by
the engine until the pinion disengages from
the flywheel.
Precautions
Further details of the various systems are
given in the relevant Sections of this Chapter.
While some repair procedures are given, the
usual course of action is to renew the
component concerned. The owner whose
interest extends beyond mere component
renewal should obtain a copy of the
“Automobile Electrical & Electronic Systems
Manual” , available from the publishers of this
manual. It is necessary to take extra care when
working on the electrical system to avoid
damage to semi-conductor devices (diodes
and transistors), and to avoid the risk of
personal injury. In addition to the precautions
given in “Safety first!” at the beginning of this
manual, observe the following when working
on the system:
Always remove rings, watches, etc before
working on the electrical system. Even with
the battery disconnected, capacitive
discharge could occur if a component’s live
terminal is earthed through a metal object.
This could cause a shock or nasty burn. Do not reverse the battery connections.
Components such as the alternator, electronic
control units, or any other components having
semi-conductor circuitry could be irreparably
damaged. If the engine is being started using jump
leads and a slave battery, connect the
batteries positive-to-positive and negative-to-
negative (see “Jump starting” ). This also
applies when connecting a battery charger.
Never disconnect the battery terminals, the
alternator, any electrical wiring or any test instruments when the engine is running.
Do not allow the engine to turn the
alternator when the alternator is not
connected. Never “test” for alternator output by
“flashing” the output lead to earth.
Never use an ohmmeter of the type
incorporating a hand-cranked generator for
circuit or continuity testing.
Always ensure that the battery negative lead
is disconnected when working on the
electrical system. Before using electric-arc welding
equipment on the car, disconnect the battery,
alternator and components such as the fuel
injection/ignition electronic control unit to
protect them from the risk of damage.
Battery disconnection
Several systems fitted to the vehicle require
battery power to be available at all times, either
to ensure that their continued operation (such as
the clock) or to maintain control unit memories
(such as that in the engine management
system’s ECU) which would be wiped if the
battery were to be disconnected. Whenever the
battery is to be disconnected therefore, first note
the following, to ensure that there are no
unforeseen consequences of this action:
a) First, on any vehicle with central locking, it is a wise precaution to remove the key
from the ignition, and to keep it with you,
so that it does not get locked in, if the
central locking should engage accidentally
when the battery is reconnected.
b) On cars equipped with an engine
management system, the system’s ECU will
lose the information stored in its memory -
referred to by Ford as the “KAM” (Keep-
Alive Memory) - when the battery is
disconnected. This includes idling and
operating values, and any fault codes
detected - in the case of the fault codes, if
it is thought likely that the system has
developed a fault for which the
corresponding code has been logged, the
vehicle must be taken to a Ford dealer for
the codes to be read, using the special
diagnostic equipment necessary for this.
Whenever the battery is disconnected, the
information relating to idle speed control
and other operating values will have to be
re-programmed into the unit’s memory.
The ECU does this by itself, but until then,
there may be surging, hesitation, erratic idle
and a generally inferior level of
performance. To allow the ECU to relearn
these values, start the engine and run it as
close to idle speed as possible until it
reaches its normal operating temperature,
then run it for approximately two minutes at
1200 rpm. Next, drive the vehicle as far as
necessary - approximately 5 miles of varied
driving conditions is usually sufficient - to
complete the relearning process.
c) If the battery is disconnected while the alarm system is armed or activated, the
alarm will remain in the same state when the battery is reconnected. The same
applies to the engine immobiliser system
(where fitted).
d) If a Ford “Keycode” audio unit is fitted,
and the unit and/or the battery is
disconnected, the unit will not function
again on reconnection until the correct
security code is entered. Details of this
procedure, which varies according to the
unit and model year, are given in the
“Ford Audio Systems Operating Guide”
supplied with the vehicle when new, with
the code itself being given in a “Radio
Passport” and/or a “Keycode Label” at
the same time. Ensure you have the
correct code before you disconnect the
battery. For obvious security reasons, the
procedure is not given in this manual. If
you do not have the code or details of the
correct procedure, but can supply proof
of ownership and a legitimate reason for
wanting this information, the vehicle’s
selling dealer may be able to help.
Devices known as “memory-savers” (or
“code-savers”) can be used to avoid some of
the above problems. Precise details vary
according to the device used. Typically, it is
plugged into the cigarette lighter, and is
connected by its own wires to a spare battery;
the vehicle’s own battery is then disconnected
from the electrical system, leaving the
“memory-saver” to pass sufficient current to
maintain audio unit security codes and ECU
memory values, and also to run permanently-
live circuits such as the clock, all the while
isolating the battery in the event of a short-
circuit occurring while work is carried out.
Warning: Some of these devices
allow a considerable amount of
current to pass, which can mean
that many of the vehicle’s
systems are still operational when the
main battery is disconnected. If a
“memory-saver” is used, ensure that the
circuit concerned is actually “dead” before
carrying out any work on it!
2 Electrical fault finding - general information
Refer to Chapter 12.
3 Battery -testing and charging
1
Standard and low maintenance
battery - testing
1If the vehicle covers a small annual mileage,
it is worthwhile checking the specific gravity
of the electrolyte every three months to
determine the state of charge of the battery.
Use a hydrometer to make the check and
compare the results with the following table.
5A•2 Starting and charging systems
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