1995 BMW M3 gravity

CHARGING
SYSTEM

TROUBLESHOOTING
.............
.
.
.
.
.121-2

Charging
System
Quick-Check
...
.
..
.
...
.
121-2

Static
current
draw,
checking
........
.
...
.
121-2

BATTERY
SERVICE
....................
121-3

Battery
Testing
.
.
.
.
.
.........
.
........
.
121-3

Hydrometer
Testing
.
...
.
.
.
...
.
.........
121-3

Battery
Open-Circuit
Voltage
Test
....
.
....
121-4

Battery
Load
Voltage
Test
.
.
.
.
.
.
.........
121-4

Battery
Charging
.
.
.
.
...
.
.
.
.
.
.
.
.........
121-4

ALTERNATOR
SERVICE
.
.
.
.
.
.
.....
.
...
121-4

Chargingsystem,checking
.
.
.
.
.
.........
121-4

Alternator,
removingand
installing

(4-cylinder
engine)
....
.
.
.
.
.
.
.
.........
121-5

Alternator,
removingand
installing

(6-cylinder
engine)
..
.
.
.
.
.
.
.
.
.
.........
121-6

GENERAL

The
charging
system
consists
of
a
belt-driven
alternator

with
integral
voltage
regulator
and
a
battery
mounted
in
the

luggage
compartment
.

Various
versions
of
alternators,
voltage
regulators,
starters,

and
batteries
are
used
in
the
E36
cars
.
It
is
important
to
re-

place
components
according
tothe
original
equipment
speci-

fication
.
Check
with
an
authorized
BMW
dealer
for
specific

application
and
parts
information
.

WARNING
-

"
Weargoggles,
rubbergloves,
and
a
rubberapron
when
working
around
batteries
and
battery
acid
(electrolyte)
.

"
Battery
acid
contains
sulfuric
acid
and
can
cause
skin
irritation
and
burning
.
ff
acid
is
spilled
onyour
skin
or
clothing,
flush
the
area
at
once
with
large
quantities
of
water
.
lf
electrolyte
gets
into
your
eyes,flush
them
with
largequantities
of
clean
wa-
terfor
several
minutes
and
call
a
physician
.

"
Batteries
that
are
being
charged
or
are
fully
charged
give
off
explosive
hydrogen
gas
.
Keep
sparks
and
open
flames
away
.
Do
not
smoke
.

BATTERY,
STARTER,
ALTERNATOR



121-1

121
Battery,
Starter,
Alternator

GENERAL
..
.
...
.
........
.
...
.
.
.
.
.
.
.
.
.
121-1



Voltage
regulator,
removing
and
ínstalling
.
.
.
121-6

Alternator
brushes,
inspecting
and
replacing
.121-7

STARTER
SERVICE
....
.
.
.
.
.
..........
.121-7

Starter
Troubleshootíng



121-7



15
..
.
.
.
.
.
........
.
.
.

Starter,
removing
and
installing

(4-cylinder
engine)
....
.
.
.
............
.
121-8

Starter,
removing
and
installing

(6-cylinder
engine
with
manual
transmission)
..
.
...........
.
...
121-8

Starter,
removing
and
installing

(6-cylinder
engine
with

automatic
transmission)
................
121-9

Solenoid
switch,
removingand
installing
....
121-10

TABLES

a
.
Battery,
Starter
and
Charging
System

Troubleshooting
............
.
.
.
.
:...
........
121-2

b
.
Specific
Gravity
of
Battery
Electrolyte
at
80°F
(27°C)
...............
.
.
..
..........
121-3

c
.
Open-Circuit
Voltage
and
Battery
Charge
........
121-4

d
.
Battery
Load
Test-Minimum
Voltage
.
..........
121-4

CAUTION
-

"
Prior
to
disconnectiog
the
battery,
read
the
bat-tery
disconnection
cautions
given
at
the
front
of
this
manual
on
page
viii
.
"
Disconnecting
the
battery
cables
may
erase
fault
codes
stored
in
control
unit
memory
.

"
Always
disconnect
the
negative
()
battery
cable
first
and
reconnect
it
last
.
Cover
the
battery
post
with
an
insulating
material
whenever
the
cable
is
removed
.

"
After
reconnecting
the
battery,
the
power
window
motors
must
be
reinitialized
.
See
511
Door
Win-
dows
.

"
Never
reverse
the
battery
cables
.
Even
a
momen-
tary
wrong
connection
can
damage
the
alternatoror
other
electrical
components
.

"
Battery
cables
may
be
the
same
color
.
Label
ca-blebefore
removing
.

GENERAL

Fig
.1.



Electrical
system
static
current
draw
being
measured
.

To
determine
the
circuit
or
component
causing
the
problem,

remove
one
Puse
at
a
time
until
the
current
drops
to
a
normal
range
.

BATTERY
SERVICE

The
E36
uses
a
six-cell,
12-volt
leadacid
battery
mounted

in
the
luggage
compartment
.
See
Fig
.
2
.

NOTE-

E36
convertible
models
require
a
specialbattery
which
is
designed
for
constant
vibratfon
.
A
battery
not
de-signed
for
this
will
fail
much
earlier
.

Battery
capacity
is
determined
by
the
amount
of
current

needed
tostart
the
vehicle,
and
by
the
amount
of
current
con-
sumed
by
the
electrical
system
.

BMW
batteries
are
rated
by
ampere/hours
(Ah)
and
cold

cranking
amps
(CCA)
rating
.
The
Ah
rating
is
determined
by

the
average
amount
of
current
the
battery
can
deliver
over
time
without
dropping
below
a
specified
voltage
.
The
CCA
is

determined
by
the
battery's
ability
to
deliver
starting
current
at

0°
F
(-18°
C)
without
dropping
below
a
specified
voltage
.

Battery
Testing

noN~A

B9517

Battery
testing
determines
the
state
of
battery
charge
.
On

conventional
or
low-maintenance
batteries
the
most
common

method
of
testing
the
battery
is
that
of
checking
the
specific

gravity
of
the
electrolyte
using
a
hydrometer
.
Before
testing

the
battery,
check
that
the
cables
are
tight
and
free
of
corro-

sion
.
See
Fig
.
2
.

Hydrometer
Testing

The
hydrometer
consists
of
a
glass
cylinder
with
a
freely

moving
float
inside
.
When
electrolyte
is
drawn
into
the
cylin-

der,
the
levelto
which
the
float
sinks
indicates
the
specific

BATTERY,
STARTER,
ALTERNATOR



121-
3

Fig
.
2
.



Battery
in
right
sideof
luggage
compartment
.

gravity
of
the
electrolyte
.
The
more
dense
the
concentration
of
sulfuric
acid
in
the
electrolyte,
the
less
the
float
will
sink,
result-

ing
in
a
higher
reading
and
indicating
a
higher
state
of
charge)
.

NOTE-

Electrolyte
temperature
affects
hydrometer
reading
.
Check
the
electrolyte
temperaturewith
a
thermometer
.
Add
0
.004
to
the
hydrometer
reading
for
every
10°F
(6°C)
that
the
electrolyte
is
above
80°F
(27°C)
.
Sub-
tract
0
.004
from
the
reading
for
every
10°F
(6°C)
that
the
electrolyte
is
below
80°F
(27°C)
.

Before
checking
the
specificgravity
of
a
battery,
load
the
battery
with
15
amperes
for
one
minute
.
lf
the
battery
is
in-

stalled
in
the
vehicle,
this
can
be
done
by
turning
on
the
head-

lights
without
the
engine
running
.
Table
b
lists
the
percentage

of
charge
based
on
specific
gravity
values
.

Table
b
.
Specific
Gravity
of
Battery
Electrolyteat

80
°
F
(27°C)

Specific
gravity



1



Stateof
charge

1
.265



Fully
charged
1
.225



75%
charged
1
.190



50%
charged
1
.155



25%
charged
1
.120



Fully
discharged

The
battery
isin
satisfactory
condition
if
theaverage
specif-

ic
gravity
of
the
six
cells
is
at
least
1
.225
.
If
the
specific
gravity

is
above
this
leve¡,
butthe
battery
lacks
power
for
starting,
de-

termine
the
battery's
senrice
condition
with
a
load
voltage
test,

as
described
below
.
If
the
average
specific
gravity
of
the
six

cells
is
below
1
.225,
remove
the
battery
from
the
luggage

compartment
and
recharge
.
If,
after
recharging,
the
specific
gravity
varies
by
more
than
0
.005
between
any
two
celis,
re-

place
the
battery
.

CHARGING
SYSTEM
TROUBLESHOOTING