MG MGB User Manual

THE
ELECTRICAL SYSTEM
N
13.3
volts.
If the
cut-in
occurs
outside
these
limits
an
adjustment
must
be
made. In
this
event
proceed
as
follows.
Remove
the
control box
cover.
Using
a
suitable
tool
(see
Fig.
N
7),
turn
the
cut-out
relay adjustment
cam
until the
correct
setting
is
obtained. Turn
the
tool clockwise
to
raise
the
setting
or
anti-clockwise
to
lower
it.
Stop
the
engine,
restore
the
original connections,
and
refit the
cover.
DROP-OFF
ADJUSTMENT
Withdraw
the
cables
from
control
box
terminal
blades
‘B’.
To
enable
the engine
to
be
started
it
will be
necessary
to
join
the ignition
and
battery
feeds
together
with
a
suitable
lead.
Connect
a
first-grade
0—20
moving-coil
voltmeter
between
control box
terminal
‘B’ and
a
good
earthing
point.
Start
the
engine
and
run
up
to
approximately 3,000
rpm.
Slowly
decelerate
and
observe
the voltmeter
pointer.
Opening
of the
contacts,
indicated by
the
voltmeter pointer
dropping
to
zero,
should
occur
between
9.5
and 11
volts.
If
the
drOp-off
occurs
outside
these
limits
an
adjustment
must
be
made.
Proceed
as
follows.
Stop
the engine
and
remove
the
control
box
cover.
Adjust
the
drop-off voltage
by
carefully
bending
the
fixed
contact
bracket.
Reducing
the
contact
gap
will
raise
the
drop-off
voltage
and increasing
the
gap
will lower it.
Retest,
and
if
necessary
readjust
until
the
correct
drop-off
setting
is
obtained.
This
should
result
in
a
contact
‘follow
through’
or
blade
de■ection
of .010
to
.020in.
(.254
to
.508
mm.).
Restore
the
original
connections
and
refit
the
cover.
Current
regulator
ON-LOAD
SETTING
The
current
regulator
on-load
setting
is
equal
to
the
maximum
rated
output
of the dynamo,
which
is
22
amps.
METHOD
OF
ADJUSTMENT
The
dynamo
must
be
made
to
develop
its maximum
rated
output
whatever
the
state
of charge
of the battery
might be
at
the
time
of
setting.
The
voltage
regulator
must
therefore
be
rendered
inoperative,
and
to
do
this the
bulldog
clip
shown in
Fig. N7
is
used
to
keep
the
voltage
regulator
contacts
together.
Remove
the
control box
cover
and,
using
a
bulldog
clip,
short
out
the
contacts
of the voltage
regulator.
Withdraw
the cables
from the
control box
terminal
blades
‘B’
and
connect
a
first-grade
0—40
moving-coil
ammeter
between
these
cables
and
one
of the
terminal
blades ‘B’. It
is important
that
terminal ‘B’
should
carry
only
this
one
connection.
All
other
load connections,
including the
ignition
coil
feed,
must
be
made
to
the battery.
Switch
on
all
lights and accessories,
start
the
engine,
and
run
the
dynamo
at
3,000
rpm.
The
ammeter
pointer
should be
steady
and
indicate
a
current
of 19—22
amps.
An
unsteady
reading
may
be
due
to
dirty
contacts.
If the reading
is
too
high
or
too
low
an
adjustment
must
be
made.
Proceed
as
follows.
Using
a
suitable tool
(see
Fig.
N.7),
turn
the
current
adjustment
cam
until the
correct
setting is
obtained. Turn
the tool
clockwise
to
raise
the
setting
or
anti-clockwise
to
lower
it.
Stop
the
engine,
restore
the
original connections,
and
re■t
the
control
box
cover.
MGB. Issues.
5335
Adjustment
of
air
gap
settings
Air
gap
settings
are
accurately
adjusted
during
manufacture
and
should
require
no
further attention.
If
the
original
settings
have been
disturbed,
it
will be
necessary
to
make
adjustments in
the
manner
described
below.
ARMATURE-TO-BOBBIN
CORE GAPS
OF
VOLTAGE
AND
CURRENT
REGULATORS
Disconnect
the battery.
Using
a
suitable
tool
(see Fig.
N.7),
turn
the adjustment
cam
of
the regulator
being
adjusted
to
the
point
giving
minimum
lift
to
the
armature
tensioning
spring
(by
turning
the
tool
to
the
fullest
extent
anti-clockwise).
Slacken
the appropriate
contact
locking
nut
and
unscrew
the
contact.
Insert
a
feeler
gauge
of .056
in.
(1.42
mm.)
thickness
between
the
armature
and the
regulator head
as
far
back
as
the
two
rivet
heads
on
the
underside
of the
armature.
With the
gauge
in
position,
press
squarely
down
on
the
armature,
and
screw
in
the
contact
until
it
just
touches
the
armature
contact.
Tighten
the
locknut
and withdraw
the
gauge.
Repeat
this
procedure
on
the
remaining
regulator.
NOTErOn
earlier
type
regulators
having
a copper
shim
on
the
regulator
head the air
gap
setting is
.045 in.
(1.15
mm.)
and
care
must
be taken
not to
damage the
copper
shim.
Carry
out
the
electrical
setting
procedure.
CONTACT
‘FOLLOW
THROUGH’ AND
ARMATURE-TO-BOBBIN
CORE
GAP OF
CUT-OUT
RELAY
Press
the
armature
squarely down against
the
copper
separation
on
the
core
face. Adjust
the
fixed
contact
bracket
to
give
a
‘follow
through’
or
blade
deflection
of
the
moving
contact
of
.010
to
.020
in.
(.254
to
.508
mm.).
Adjust
the
armature
back
stop to
give
a
core
gap
of .035
to
.045
in.
(.889
to
1.147
mm.).
Check
the
cut-in
and
drop-off voltage
settings.
Cleaning
contacts
REGULATOR
CONTACTS
To
clean the
voltage
or
current
regulator
contacts
use
fine
carborundum
stone
or
silicon-carbide
paper,
followed by
methylated
spirit
(denatured
alcohol).
CUT-OUT
RELAY
CONTACTS
To
clean
the
cut-out
relay
contacts
use a
strip
of fine
glass-paper—never
carborundum
stone
or
emery-cloth.
Section N.6
STARTER
Testing
on
vehicle when
starter
is
not
operating
In
the
following
test
it
is
assumed that the battery
is in
a
charged condition.
Switch
on
the
lamps and
operate
the
starter
control.
If the
lights
go
dim but the
starter
is
not
heard
to operate,
an
indication
is given
that the
current
is
■owing through the
starter motor
windings, but that for
some
reason
the
armature
is
not
rotating;
possibly the
starter
pinion
is
N.9

MG MGB Specifications

General

Brand	MG
Model	MGB
Category	Automobile
Language	English