Owners Manual
ELECTRICAL
EQUIPMENT
0/19
LOCATION AND REMEDY
OF
FAULTS
Although every precaution is taken to eliminate
all possible causes
of
trouble, failure may occasionally
develop through lack
of
attention to the equipment,
or damage to the wiring. The following pages set out
the recommended procedure for a systematic examina-
tion to locate and remedy the causes
of
some
of
the more
probable faults. The sources of many troubles are
by
no means obvious and
in
some cases a considerable
amount of deduction from the symptoms
is
needed
before the cause of the trouble
is
disclosed.
For instance, the engine might not respond to the
starter switch; a hasty inference would be that the
starter motor is
at
fault. However,
as
the motor
is
dependent on the battery,
it
may be that the battery
is
exhausted.
This,
in
turn, may be due to the dynamo failing
to charge the battery, and the final cause
of
the trouble
may be, perhaps, a loose connection in some part of the
charging circuit,
If,
after carrying out the examination, the cause
of
the trouble is
not
found,
it
is advisable to consult
the nearest Lucas
Service Depot or Agent.
IGNITION CIRCUIT
1. Engine will not fire
(a)
See
that the battery terminals are secure and that
the battery
is
in a charged condition, either by use of
a hydrometer or
by
checking that the starter will turn
the engine and the lamps give a good light.
If
the battery is discharged,
it
must be recharged
from an independent electrical supply.
(b)
See
that the controls are correctly set for starting.
(c)
Remove the cable from the centre distributor term-
inal and hold it
so
that the end is about i-in. away from
some metal part
of
the chassis while the engine
is
turned
slowly over.
If
sparks jump the gap regularly, the coil
and distributor are functioning correctly, and the spark-
ing plugs must be examined.
If
these are clean, and the
gaps correct, the trouble
is
due to carburetter, petrol
supply, etc.
(d)
Ifthe
coil does not spark in test
(c)
check for a
fault in the low tension wiring. This will be indicated
by
(i) no ammeter reading when the engine
is
slowly
turned and the ignition switch is on, or
(ii) no spark occurring between the distributor con-
tacts when quickly separated
by
the fingers when
the ignition is switched on. Examine all cables in
the ignition circuit and see that all connections are
tight.
(e)
If
the wiring proves to be in order examine the
distributor contacts,
if
necessary cleaning them and
adjusting the gap
as
described on page 0/1.
2. Engine Misfires
(a) Examine the distributor contacts,
if
necessary
cleaning them and adjusting the gap
as
described on
page
0/1.
(b)
Run the engine at a fairly fast idling speed and
short-circuit each plug in turn with, say, the blade of
an
insulated screwdriver, or with a hammer head placed
across the plug terminal to contact the cylinder head.
Short-circuiting a defective plug will cause no
noticeable change
in
the running note, whereas shorting
out a sound plug will cause a pronounced increase in
roughness.
(c)
Having thus located the defective cylinder, stop
the engine and remove the cable from the sparking plug
terminal. Re-start the engine and hold the cable end
about
{
6
-in. (4.
7625
mm.) from the cylinder head.
If
the sparking
is
strong and regular, the fault lies with
the sparking plug which should be removed, cleaned
and adjusted, or replaced.
(d)
If,
however, there is no spark or only weak and
irregular sparking, examine the cable from the plug to the
distributor, renewing the cable
if
the rubber
is
cracked
or perished. Clean the distributor moulded cover and
check the free movement
of
the carbon brush.
If
this
brush needs replacing
see
that
the correct type is ob-
tained; the standard non-resistive brush
is
too short
for use with model DM2AH4 distributor and would
not
make contact with the rotating electrode.
If
track-
ing has occurred, indicated by a thin black line, usually
between two or more electrodes, a replacement distri-
butor cover must be fitted.
(e)
If
test
(b)
shows all four plugs to be sparking
regularly, the trouble may be due to engine defects or
to the carburetter, petrol supply, etc.
CHARGING CIRCUIT
1. Battery in a
low
state
of
charge
(a)
This state will be shown by lack
of
power
when
starting, poor light from the lamps, and hydrometer
readings below 1 .
200,
and may be due to the dynamo
either not charging or giving low or intermittent output.
The ignition warning light will not
go
out
if
the dynamo
fails to charge, or will flicker on and off in the event of
intermittent output.
(b)
Examine the charging and field circuit wiring,
tightening any loose connection, or replacing broken
cables.
Pay particular attention to the battery con-
nections.
(c)
Examine the dynamo driving belt; take up any un-
due slackness
by
turning the dynamo on its mounting.
(d)
If
the cause ofthe trouble
is
not apparent, have the
equipment examined
by
a Lucas Service Depot or Agent.