MG MGB User Manual

THE
ELECTRICAL
SYSTEM
N
2.
If
any
parts
are
worn or
damaged
they
must
be
renewed.
COMMUTATOR
A
commutator
in
good
condition
will be
smooth and
free
from
pits
and burned
spots. Clean
the
commutator
with
a
cloth
moistened with
petrol
(gasoline).
If this
is
ineffective
carefully
polish
with
a
strip
of ■ne glass-paper
while
rotating
the
armature.
To
remedy
a
badly
worn
commutator
dismantle the
starter
drive
as
described above
and
remove
the
armature
from
the end
bracket.
Now
mount
the
armature
in
a
lathe,
rotate
it
at
a
high
speed,
and
take
a
light
cut
with
a
very
sharp
tool. Do
not
remove any
more
metal
than
is
absolutely
necessary,
and
finally
polish
with
very
■ne glass-paper.
The
mica
on
the
starter
commutator
must not
be
undercut.
FIELD
COILS
The
■eld
coils
can
be
tested
for
an
open
circuit
by
connecting
a
12-volt battery,
having
a
12-volt
bulb
in
one
of the
leads,
to
the tapping-point
of the field
coils
to
which
the
brushes
are
connected
and
the
■eld terminal
post.
If the
lamp
does
not
light there is
an
open
circuit in
the
wiring
of
the
■eld coils.
Lighting
of the
lamp does
not
necessarily
mean
that
the
field coils
are
in
order
as
it is
possible
that
one
of them
may
be
earthed
to
a
pole-shoe
or
to
the
yoke.
This
may
be
checked
by
disconnecting
the battery
lead from
the
tapping-point
of
the
■eld
coils
and holding
it
on a
clean
part
of
the
starter
yoke.
Should the
bulb
now
light,
it
indicates
that
the field
coils
are
earthed.
_
NOTE—When carrying
out
this
test
the
brushes
connected
to
the
field coils
must not
be in
contact
with
the
starter
yoke.
7
Should the
above
tests
indicate
that the
fault lies
in
the
field coils,
they
must
be
renewed.
When renewing
■eld coils
carry
out
the
procedure
detailed
in
Section
N.4.
_/
Will
\\\\\\\\
,A,
////
I750.
Fig.
N.9
The
starter
brush
connections.
A, Brushes_
B.
Tapping
on
field
coils.
MGB.
Issue4.
25729
Fig. N.l
0
Fitting
a
new
bush,
using
a
shouldered
mandrel
A.
Hand
press.
B.
Bearing
bush.
C.
Supporting
block.
D.
Shouldered
mandrel.
ARMATURE
Examination
of the
armature
will
in
many
cases
reveal
the
cause
of failure,
e.g.
conductors
lifted
from
the
commutator
due
to
the
starter
being
engaged while the
engine is
running
and causing
the
armature to
be
rotated
at
an
excessive
Speed.
A
damaged
armature
must
in
all
cases
be
renewedrno
attempt
should be
made
to
machine
the
armature
core
or
to true
a
distorted
armature
shaft.
BEARINGS
(COMMUTATOR
END)
Bearings
which
are
worn
to
such
an
extent
that
they will
allow
excessive
side-play
of the
armature
shaft
must
be
renewed. To
renew
the bearing
bush proceed
as
follows.
Press the
new
bearing
bush
into
the
end
bracket, using
a
shouldered mandrel
of
the
same
diameter
as
the
shaft which
is
to
■t
in
the bearing.
NOTE—The bearing
bush
is
of
the
porous
phosphor-bronze
type,
and
before
fitting,
new
bushes
should
be
allowed
to
stand completely
immersed
for
24
hours in
thin engine
oil
in
order
to
fill the
pores
of
the
bush with lubricant.
REASSEMBLING
The
reassembly
0f the
starter
is
a
reversal of the
operations
described
in
this Section.
Section
N.7
FUSES
The
fuses
are
mounted
in
a
separate
holder located under
a
'large
plastic
cover on
the
right-hand
wing
valance.
if
N. 1
3

MG MGB Specifications

General

Brand	MG
Model	MGB
Category	Automobile
Language	English