wire BMW 318i 1997 E36 Owners Manual

515-2



CENTRAL
LOCKING
AND
ANTI-THEFT

0013117

Fig
.
1
.



4-door
cars
:
Remove
lower
retaining
boltat
base
of
window
rear
guide
rail
and
pivot
rail
out
of
door
.

Fig
.
3
.



Front
door
lock
mounting
screws
(arrows)
.

uu11686
0012685

Fig
.
4
.



Pry
out
locklinkage
(A)
from
plastic
retainer
.
Lift
door
lock
mechanism
slightly
to
Rmove
latching
pin
from
lock
gate
(B)
.
Door
lock
mechanism
shown
removed
from
door
.
0013073
Fig
.
2
.



Inside
door
handle
retaining
screw
(A)
Unhook
linkage
from
handle
at
B
.



9
.
Installation
is
reverse
of
removal,
noting
the
following
:

DOOR
HANDLES
AND
LOCKS

"
Install
lock
mounting
bolts
with
Loctite
0
270
or
equiva-
lent
thread-locker
.
"
Reconnect
power
window
motor
harness
connector
.
"
Usenew
mounting
bolts
when
reinstalling
the
side-ím-
pact
airbag
to
the
door
(where
applicable)
.
"
Secure
wire
harnesses
with
wire
ties
.
"
Check
function
of
door
lock
and
window
mechanism

before
reinstalling
inner
door
panel
.

Tightening
Torques

"
Door
lock
to
door
......
.
..........
9
Nm
(80
in-lb)

"
Window
guide
to
door
........
.
...
10
Nm
(89
in-lb)

515-4



CENTRAL
LOCKING
AND
ANTI-THEFT

11
.
Installation
is
reverse
of
removal
.
Keep
in
mind
the
fol-



4
.
Remove
screws
mounting
bottom
of
window
rear
track

lowing
:



to
door
.
See
Fig
.
9
.

"
Make
sure
rubber
seal
for
handle
is
correctly
posi-

tionedbefore
tightening
mounting
fasteners
.

"
Install
exteriortrim
piece
and
then
use
a
hooked
tool
to

pull
locking
plate
into
locked
position
.
Make
sure
door

handle
trim
contacts
body
evenly
before
locking
trim

in
place
.

"
Use
new
mounting
bolts
when
reinstalling
the
side-im-

pactairbag
to
the
door(where
applicable)
.
Reset
SRS

warning
light
and
clear
SRS
fault
memory
using
spe-

cial
test
equipment
.
See
721
Airbag
System
(SRS)
.

"
Reconnect
al¡
harness
connectors
(including
power

window
motor)before
installing
door
panel
.

"
Secure
wire
harnesses
withwire
ties
.

"
Adjust
and
reinitialize
windows
.
See
512
Door
Win-

dows
.

Tightening
Torque

"
Collar
nut
to
doorhandle
..........
10
Nm
(89
in-lb)

1.
Remove
rear
door
panel
and
vapor
barrier
as
described

in
411
Doors
.

2
.
Remove
window
from
rear
dooras
described
in
512

Door
Windows
.

3
.
Disconnect
andremove
inside
door
handle
.
See
Fig
.
8
.

0013073

Fig
.
8
.



Inside
door
handle
retaining
screw
(A)
Unhook
linkage
from
handle
at
B
.

DOOR
HANDLES
AND
LOCKS

Fig
.
9
.



Rear
window
track
lower
fasteners
(arrows)
.

Reardoor
lock,
removing
and
installing



5
.
Remove
window
rear
track
top
screw
and
move
track

aside
.
See
Fig
.
10
.

Fig
.
10
.
Rear
window
track
top
screw
(arrow)
.

6
.
Remove
screw
from
lock
button
linkage
rod
retainer
.
Lift

rod
out
of
retaining
clip
.
See
Fig
.
11
.

7
.
Disconnect
door
lock
harnessconnector
.

8
.
Remove
door
lock
screws
.
See
Fig
.
12
.

0013085

9
.
Move
lock
upslightly
to
disengage
from
exterior
handle

linkage
.
Remove
lock
from
inside
door
.

0011688

Fig
.
11
.
Rear
door
lockbutton
linkage
rod
retainer
(A),
rod
retaining
clip
(B),
and
harness
connector
(C)
.

Fig
.
12
.
Rear
door
lock
mounting
screws
(arrows)
.

0011687

10
.
Installation
is
reverse
of
removal
.
Keep
in
mind
the
fol-
lowing
:

"
Insta¡¡
lock
mounting
boits
with
Loctite
©
270
or
equiva-

lentthread-locker
.

"
Reconnect
power
window
motorharness
connector

before
installing
door
panel
.

"
Secure
wire
harnesses
with
wire
ties
.

"
Adjust
window
as
described
in
512
Door
Windows
.

Tightening
Torque

"
Door
lock
to
door
.
...
.
..
..........
9
Nm
(80
in-lb)

CENTRAL
LOCKING
AND
ANTI-THEFT



515-5

Rear
door
handie,
removing
and
installing

1
.
Remove
rear
door
panel
and
vapor
barrier
as
described
in
411
Doors
.

2
.
Remove
window
from
rear
door
as
described
in
512

Door
Windows
.

3
.
Remove
door
lock
as
described
earlier
.

4
.
Pry
out
access
plug
in
end
of
door
.
Use
screwdriver
through
access
hole
to
slide
exterior
trim
locking
plate
into
released
position
.
See
Fig
.
13
.
Remove
doorhan-
dle
exterior
trim
piece
.

u
.]lbbl

Fig
.
13
.
Insert
screwdriver
into
access
hole
and
push
locking
plate
forward
(arrow)torelease
exterior
handle
trim
.

5
.
Remove
door
handle
mountingscrews
while
support-

ing
handle
.
See
Fig
.
14
.

Fig
.
14
.
Reardoor
handle
mounting
screws
(arrows)
.

0011684

DOOR
HANDLES
AND
LOCKS

515-6



CENTRAL
LOCKING
AND
ANTI-THEFT

6
.
Remove
door
handle
assembly
from
inside
door
.

7
.
Installation
is
reverse
of
removal
.
Keep
in
mindthe
fol-

lowing
:

"
Make
sure
rubber
seal
for
handle
is
correctly
posi-

tionedbefore
tightening
mounting
fasteners
.

"
Install
exterior
trim
piece
and
then
use
a
hooked
toolto

pull
locking
plate
into
locked
position
.
Make
sure
door
handle
trim
contacts
body
evenly
before
lockingtrim

in
place
.

"
Reconnect
all
harness
connectors
(including
power

window
motor)before
installing
door
panel
.

"
Secure
wire
harnesses
withwire
ties
.

"
Adjust
windowas
described
in
512
Door
Windows
.

Tightening
Torque

"
Rear
door
handle
mounting
screws
..
10
Nm
(89
in-lb)

NOTE

If
the
striker
backup
plate
fafls
into
the
body
cavlty,
it
can
be
retrieved
after
removing
the
inside
trim
from
the
B-pillar
(door-post
pillar)
.

Tightening
Torque

"
Striker
plate
to
body
pillar
..........
28
Nm
(20
ft-lb)

LOCKING
ACTUATORS

Door
Locking
Actuator

The
front
door
lock
mechanism
and
actuator
are
shown
in
Fig
.
15
.
The
rear
door
lock
and
actuator
are
similar
.
The
lock
must
first
be
removed,
as
described
earlier,
to
replace
the
ac-
tuator
.

if
defective
.

LOCKING
ACTUATORS

Connections
to
door
handle

®
o

_



Attaching
pin
0

O~
Lock
mechanism

0012082

Fig
.
15
.
Front
door
lock
mechanism
and
related
parts
.
Rear
lock
mechanism
is
similar
.

Door
striker,
replacing



Luggage
compartment
locking
actuator,

removing
and
installing
The
door
striker
contains
an
electrical
contact
switch
.
If
the

switch
is
faulty,
the
striker
must
be
replaced
.
To
remove
the



1
.
Raise
trunk
lid
.
Remove
tool
kit
and
trunk
lid
trim
panel
.

striker,
remove
the
mounting
bolts
.
Disconnect
the
harness



See
Fig
.
16
.

connector
from
the
striker
.

0013162

Fig
.
16
.
Trunk
lid
trim
and
tool
kit
retainíng
screws
and
clips
(arrows)
.

2
.
Disconnect
actuating
rod
from
lock
.
See
Fig
.
17
.

3
.
lJnplug
two
wíring
connectors
from
actuator
.
See
Fig
.

18
.

NOTE
-

"
lf
just
one
of
the
centrallocking
drives
does
not
oper-



NOTE-

ate,
the
lockinglinkage
could
be
frozen
orstiff
enough



The
actuator
is
adjustable
.
Matchmark
the
attaching
to
prevent
actuatonof
the
drive
.
Try
remove
the
finte-



screws
before
removal
.

rior
doorpanel
and
lubricating
the
locking
linkage
as
the
first
step
.



4
.
Remove
actuator
attaching
screws
.
Pull
actuator
back-

"
The
actuator
is
not
serviceable
and
mustbe
replaced



wards
from
behind
metal
shield
to
remove
.

5
.
installation
is
reverse
of
removal
.
Align
actuator
screws
with
matchmarks
during
installation
.

002262



In
this
system,
three
microswitches
are
operated
via
the
door
lock
cylinder
at
each
front
door
.
Turning
the
key
approximately
Fig
.
17
.
Pufl
off
luggage
compartment
lock
actuating
rod
in
the
direc-



45°
(position
1)
operates
the
door
locking
microswitch
.
Tuming
tionof
arrow
.



the
key
approximately
90°
(position2)
actuates
the
double
locking
microswitch
.
Tuming
the
key
approximately
45°
in
the
opposite
di-
rection
through
position
0
actuates
the
unlocking
microswitch
and
deactivates
the
alarm
system
(position3)
.
See
Fig
.
19
.

Fig
.
18
.
Luggage
compartment
actuatorwire
connectors
and
attach-
ing
screws
(arrows)
.

LOCKING
SYSTEM
AND

ELECTRONIC
IMMOBILIZATION

The
central
locking
system
uses
electrical
lock
actuators
at

each
door
and
at
the
trunk
lid
.
The
locking
system
can
be
ac-

tuated
by
either
front
door
lock
or
by
the
luggage
compartment

lock
.
Onsome
1994
and
later
cars,
an
additional
remote
con-

trol
keypadcan
also
be
used
to
activate
the
lock
and
anti-theft

systems
.

When
the
key
is
tuned
to
the
lock
position,
a
micro-switch

signals
a
central
control
module
to
lock
all
doors,
luggage

compartment,
gas
tank
flap
and,
in
later
convertibles,
the

glove
box
lid
.
Where
applicable,
this
also
arms
the
anti-theft

system
.

CENTRAL
LOCKING
AND
ANTI-THEFT



515-7

NOTE-

The
central
locking
system
responds
to
accidents
vía
animpact
(inertia)
switch
.
When
this
function
ís
activat-
ed,
the
doors
are
automatically
unlocked
and
the
haz-
ard
warning
lights
and
interiorlights
are
turned
on
.
The
impact
switches
are
mounted
in
the
left
and
right
foot-
wells
behind
the
speaker
grilles
.

Central
Locking
System
(ZVM)

Different
versions
of
the
central
locking
control
havebeen
used
in
the
E36
cars
.
In
early
production
cars
(model
years
1992
and
1993),
the
locking
system
is
controlled
through
the
central
locking
module
.
This
system
is
referred
to
as
ZVM
.

Fig
.
19
.
ZVM
door
lock
cylinderpositíons
.

CAUTION-

Do
not
engage
double
locking
position
with
pas-
sengers
in
the
car
unless
the
master
key
isavail-
able
.
The
door
cannotbe
opened
from
outside
orinside
without
the
master
key
.

NOTE-

In
case
of
a
discharged
battery,
the
car
can
still
be
locked
orunlocked
using
the
key
.

0011762

LOCKING
SYSTEM
AND
ELECTRONIC
IMMOBILIZATION

515-10



CENTRAL
LOCKING
AND
ANTI-THEFT

EWS
II
control
module,
replacing

1
.
Disconnect
negative
(-)
cable
from
battery
.

CAUTION-

Prior
to
disconnecting
the
battery,
read
the
battery

disconnection
cautions
given
at
the
front
of
this
manual
onpage
vüf
.

2
.
Remove
glove
compartment
as
described
in
513
Inte-

rior
Trim
.

3
.
Remove
EWS
II
control
module
harness
connector
.

Pull
module
out
of
bracket
.
See
Fig
.
22
.

NOTE-

The
EWS
11
module
should
be
identified
with
EWS
11
markings
.

4
.
Installation
is
reverse
of
removal
.

Ring
antenna,
replacing



4
.
Cut
off
wire
ties
holding
wiring
harness
to
steering
col-

umn
.
1
.
Disconnect
negative
(-)
cable
from
battery
.

CAUTION
-

Prior
to
disconnecting
the
battery,
read
the
battery

disconnectioncautionsgiven
at
the
front
of
this
manualonpage
viii
.

2
.
Remove
lower
steering
column
cover
.
See
Fig
.
23
.

Transmitter/

receiver
Ring

r
module
antenna

Fig
.
22
.
Location
of
EWS
II
components
.

LOCKING
SYSTEM
AND
ELECTRONIC
IMMOBILIZATION

Fig
.
23
.
Steering
column
cover
retaining
screw
(arrow)
.

5
.
Gently
pry
off
ring
antenna
from
ignition
switch
.

7
.
Installation
is
reverse
of
removal
.

0012543

3
.
Remove
lower
left
dash
trim
panel
as
described
in
513

Interior
Trim
.

6
.
Unplug
ring
antennaharness
from
EWS
II
transmit-

ter/receiver
module
as
described
below
.

520-2



S
EATS

Fig
.
2
.



Frontseat
front
mounting
nut
(arrow)
.

FRONT
SEA
TS

0013166

5
.
On
2-door
cars
:
unhook
seat
belt
from
guide
on
seat

back
.

8
.
Remove
seatfrom
car
.

Fig
.
3
.



Seat
belt
mounting
bolt
(arrow)
.

0013216

9
.
Installation
is
reverse
of
removal
.
Keep
the
following
in

mind
:

6
.
Tilt
seat
back
to
access
and
unplug
electrical
harness



"
Use
wire
ties
orequivalent
means
to
keep
seat
har
connectors
.
Cut
or
untwist
wire
ties
as
necessary
.



ness
wiring
from
being
exposed
to
fraying
.
"
Reactivate
front
seat
belt
locks
.
7
.
On
4-door
cars
:
Unbolt
seat
belt
from
seat
frame
.
See



"
Start
all
seat
mounting
boits
.
Fig
.
3
.



"
Tighten
seat
mounting
fasteners
in
thís
sequence
:
in-
ner
front
;
outer
front
;
inner
rear,
outer
rear
.

Tightening
Torque

"
Front
seat
to
floor



........
.......
55
Nm
(41
ft-Ib)

600-2



ELECTRICAL
SYSTEM-GENERAL

CAUTION
-

"
Always
turn
off
the
engine
and
disconnect
the

negative
()
cable
from
the
batterybefore
remov-

ing
any
electrical
components
.
Disconnecting
the

battery
may
erase
fault
code(s)
stored
in
control

module
memory
.
Check
for
fault
codes
using
spe-
cial
BMW
diagnostic
equipment
.

"
Prior
to
disconnecting
the
battery,
read
the
bat-

tery
disconnection
cautions
given
at
the
front
of

this
manual
onpage
viii
.

"
Connect
and
disconnect
ignition
system
wires,
multiple
connectors,
and
ignition
test
equipment
leads
only
while
the
ignition
is
off
.

"
Do
not
disconnect
the
battery
with
engine
run-

ning
.

"
Do
not
quick-charge
the
battery
(for
boost
start-
ing)
for
longer
than
one
minute,
and
do
not
ex-
ceed
16
.5
volts
at
the
battery
with
the
boosting
cables
attached
.
Wait
at
feast
one
minute
before
boosting
the
battery
a
second
time
.

"
Do
not
usea
test
famp
that
has
a
normal
incan-

descent
bulb
to
test
circuits
contafning
electronic
components
.
The
high
electrical
consumptionof
these
test
lamps
may
damage
the
components
.

"
Do
not
use
an
analog
meter
.
Use
onfy
a
digital
multimeter
.

"
Many
of
the
solid-state
modules
are
static
sensi-
tive
.
Static
discharge
will
permanently
damage
them
.
Always
handle
the
modules
using
proper
static
prevention
equipment
and
techniques
.

"
To
avoid
damaging
harness
connectors
or
relay
panel
sockets,
use
jumper
wires
with
flat-blade
connectors
that
are
the
same
size
as
the
connec-
tor
or
relay
terminals
.

"
Always
switch
a
digital
multimeter
to
the
appropri-
ate
function
and
range
before
making
test
con-
nections
.

"
Do
not
tryto
start
the
engine
of
a
carwhich
has
been
heated
above176°F
(80°C),
(for
example,
in
a
paint
dryingbooth)
.
Allow
it
to
cool
to
normal
temperature
.

"
Disconnect
the
battery
before
dolng
any
electric
welding
on
the
car
.

"
Do
not
wash
the
engine
while
it
is
runnfng,
or
any-
time
the
ignition
is
switched
on
.

WIRING
DIAGRAMS

Electrical
Test
Equipment

Many
of
the
electrical
tests
described
in
this
manual
call
for

measuring
voltage,
currentorresistanceusing
a
digital
multi-

meter
(DMM)
.
Digital
meters
are
preferred
for
precise
mea-

surements
and
for
electronics
work
because
they
are
generally
more
accuratethan
analog
meters
.
The
numerical

display
is
alsoless
likely
to
be
misread,
since
there
is
no
nee-

dle
position
to
be
misinterpreted
by
reading
at
an
angle
.

An
LED
test
light
is
a
safe,
inexpensive
tool
that
can
be
used

to
perform
many
simple
electrical
tests
that
would
otherwise

require
a
digital
multimeter
.
The
LED
indicates
when
voltage

is
present
between
anytwo
test-points
in
a
circuit
.

CA
UTION-

"
Choose
test
equipment
carefully
.
Use
a
digital

multimeter
with
at
leadt
10
megaohm
input
im-

pedance,or
an
LED
test
light
.
An
analog
meter
(swing-need1e)
ora
test
light
with
a
normal
incan-
descent
bulb
may
draw
enough
current
to
dam-
age
sensitive
electronic
components
.

"
An
ohmmeter
must
not
beused
to
measure
resis-
tance
on
solidstate
components
suchas
controlunits
or
time
delay
relays
.

"
Always
disconnect
the
battery
before
making
re-

sístance
(ohm)
measurements
on
the
circuit
.

WIRING
DIAGRAMS

The
wiring
diagrams
shown
in
Electrical
Wiring
Diagrams

have
been
specially
designed
to
enable
quick
and
efficientdi-

agnosis
and
troubleshooting
of
electrical
malfunctions
.

Wiring
Codes
and
Abbreviations

A
lot
of
information
is
included
in
each
wiring
diagram
if
you
know
how
to
read
them
.
Wire
colors
in
the
diagrams
are
ab-

breviated
.
Combined
color
codes
indicate
a
multi-colored
wire
.
For
example
the
code
BLU/RED
indicates
a
Blue
wire

with
a
Red
stripe
.

Many
electrical
components,
connectors,
fuses,
and

ground
locations
are
identified
using
a
unique
number
.
Each

of
there
numbers
corresponds
to
a
particular
part
in
the
circuit
commonly
found
in
Electrical
Wiring
Diagrams
.

NOTE
-

Sometimes
the
color
of
en
installed
wire
may
be
differ-
ent
than
the
one
on
the
wiring
diagram
.
Don't
be
con-
cerned
.
Just
be
sure
lo
confirm
that
the
wire
connects
lo
the
proper
terminals
.

Wire
color
codes

"
BLU
.........
.
..
..
...
.
.................
Blue

"
BRN
....:....
.
..
..
...
..
...............
Brown

"
YEL
.........
.
..
..
...................
.Yellow

"
GRN
.........
.
..
..
...
.
................
creen

"
G
RY
.......
.
.
.
..
..
.....................
G
ray

"
ORG
.........
.
..
..
...
.
..............
.Orange

"
RED
......
...
.
.
..
.....................
.Red

"
BLK
.........
.
..
..
...
.
................
Black

"
VIO
..........
.
..
...
..
..
.......
.
.......
Violet

"
WHT
.........
.
.
....
.
...
:..............
White

Table
a
.
Terminal
and
Circuit
Numbers

Number



1
Circuít
description

1



j
Low
voltage
switched
terminal
of
coi¡

4



1
High
voltage
center
termina¡
of
coi¡

+x



Originates
atignition
switch
.
Supplies
powerwhen
the
ignition
switch
is
in
the
PARK,
RUN,
or
START
position

15



Originates
atignition
switch
.
Supplies
powerwhen
ignition
switch
is
in
RUN
or
START
position

30



Battery
positive
(+)
voltage
.
Supplies
power
whenever
battery
is
connected
.
(Not
dependent
on
ignition
switch
position,
unfused)

31



1
Ground,
battery
negative
(-)
terminal

50



Supplies
power
from
battery
to
starter
solenoid
when
ignition
switch
isin
START
position
only

+54



Originates
atignition
switch
.
Supplies
power
when
ignition
switch
isin
the
RUN
position
only

85



1
Ground
side
(-)
ofrelay
coil

86



1
Power-in
side
(+)
ofrelay
coil

87



1
Relay
actuatedcontact

D



Alternator
warning
light
and
field
energizing
circuit

ELECTRICAL
SYSTEM-GENERAL
600-
3

Additional
abbreviations
shown
in
the
wiring
diagrams
are

given
below
.

Abbreviations

"
ABS
........
.
...
.
...
.
..........
antilock
brakes

"
A/C
........
.
...
..
..
.
.........
.airconditioning

"
AST/ASC+T
.......
...
.
.
.......
al¡
season
traction

"
CONV
.......
.
.
...
.................
convertible

"
DME
........
.
.
...
.......
digital
motor
electronics

"
ECM



.......
.
...
..
..
.
..
electronic
control
module

"
EWS/EWS
II
......
...
.
.
coded
driveaway
protection

"
SRS
........
.
supplemental
restraint
system-airbag

"
TCM
........
.
..
....
.
transmission
control
module

"
ZKE
(94-98
models)
..
..
.
...
central
body
electronics

"
ZVM
(92-93
models)
...
.
.
..
.
.......
central
locking

ELECTRICAL
TROUBLESHOOTING

Most
terminals
are
identified
by
numbers
on
the
compo-

nents
and
harness
connectors
.
The
terminal
numbers
for
ma-



Four
things
are
required
for
current
toflow
in
any
electrical

jor
electrical
connections
are
shown
in
the
diagrams
.
Though



circuit
:
a
voltagesource,
wires
or
connections
to
transport
the

many
terminal
numbers
appear
only
once,
severa¡other
num-



voltage,
a
load
or
device
that
uses
the
electricity,
and
a
con-
bers
appear
in
numerous
places
throughout
the
electrical
sys-



nection
to
ground
.
Most
problemscanbefound
using
a
digital

tem
and
identify
certain
types
ofcircuits
.
Some
of
the
most



multimeter
(volt/ohm/amp
meter)to
check
for
voltage
supply,

common
circuit
numbers
are
listed
below
in
Table
a
.



for
breaks
in
the
wiring
(infinite
resistance/no
continuity),
orfor

a
path
to
ground
that
completesthe
circuit
.

Electric
current
is
logical
in
its
flow,
always
moving
from
the

voltage
sourcetoward
ground
.
Electricalfaults
can
usually
be

located
through
a
process
of
elimination
.
When
troubleshoot-

ing
a
complex
circuit,
separate
the
circuit
into
smaller
parts
.

The
general
testsoutlined
below
may
be
helpful
in
finding

electrical
problems
.
The
information
is
most
helpful
when

used
with
the
wiring
diagrams
.

Be
sure
to
analyze
the
problem
.
Use
the
wiring
diagrams
to

determine
the
most
likely
cause
.
Getan
understanding
of
how

the
circuit
works
by
following
the
circuit
from
groundback
to

the
power
source
.

When
making
test
connections
at
connectors
andcompo-

nents,
use
care
to
avoidspreading
or
damaging
the
connec-

tors
or
terminals
.
Some
tests
may
require
jumper
wires
to

bypass
components
or
connections
in
the
wiring
harness
.

When
connecting
jumper
wires,
use
bladeconnectors
at
the

wire
ends
that
match
the
size
of
the
terminal
being
tested
.
The

small
interna¡
contacts
are
easily
spread
apart,
and
this
can

cause
intermittent
or
faultyconnections
that
can
leadto
more

problems
.

ELECTRICAL
TROUBLESHOOTING

600-
4



ELECTRICAL
SYSTEM-GENERAL

Voltage
and
Voltage
Drops

The
wires,
connectors,
and
switches
that
carry
current
are

designed
with
very
low
resistance
so
that
current
flows
with
a

minimum
loss
of
voltage
.
A
voltage
drop
is
caused
by
higher
than
normal
resistance
in
a
circuit
.
This
additional
resistance

actually
decreases
or
stops
the
flow
of
current
.
A
voltage
drop

can
be
noticed
byproblems
ranging
fromdim
headlights
to
sluggish
wipers
.
Some
common
sources
of
voltage
drops
are
corroded
or
dirty
switches,
dirty
or
corroded
connections
or

contacts,
and
loose
or
corroded
ground
wires
and
ground
con-

nections
.

A
voltage
drop
test
is
a
good
test
to
make
if
current
is
flowing
through
the
circuit,
butthe
circuit
is
not
operating
correctly
.
A
voltage
drop
test
will
help
to
pinpoint
a
corroded
ground
strap
or
a
faulty
switch
.
Normally,
there
should
be
less
than
1
volt

drop
across
most
wires
or
closed
switches
.
A
voltage
drop
across
a
connector
or
short
cable
shouldnot
exceed
0
.5
volts
.

Voltage,
measuring

1
.
Connect
digital
multimeternegative
lead
to
a
reliable
ground
point
oncar
.

NOTE-

The
negative
(-)
battery
terminal
is
alwaysa
good
ground
point
.

2
.
Connect
digital
multimeter
positive
lead
to
point
incir-
cuit
you
wish
to
measure
.
See
Fig
.
1
.
If
a
reading
is
ob-
tained,
current
is
flowing
through
circuit
.

NOTE-

The
voltage
reading
shouldnot
deviate
more
than
1
volt
from
the
voltage
at
the
battery
.
If
the
voltage
drop
is
more
than
this,
check
for
acorroded
connector
or
cose
ground
wire
.

ELECTRICAL
TROLIBLESHOOTING

from
Battery

Fig
.
1
.



Digital
multimeterbeing
used
to
test
voltage
.

No
voltage
r_l

-1
Load

LJ

Switch

NOTE-

The
maximum
voltage
drop
in
an
automotive
circuit,
as
recommended
by
the
Society
of
AutomotiveEngineers
(SAE),
is
as
follows
:
0
voltsfor
small
vire
connections
;
0
.1
Volts
for
high
current
connections
;
0
.2
volts
for
high
current
cables
;
and
0
.3volts
for
switch
or
solenoidcon-
tacts
.
On
longer
wires
or
cables,
the
drop
may
be
slight-ly
higher
.
In
any
case,
a
voltage
drop
of
more
than
1.0volt
usually
indicates
a
problem
.

0013238

NOTE-

"
A
voltage
drop
test
is
generally
more
accuratethan
a



Voltage
drop,
testing

simple
resistance
check
because
the
resistances
in-
volvedare
often
too
small
to
measure
with
most
ohm-



Voltage
drop
can
only
be
checked
when
current
is
running
meters
.
For
example,
a
resistance
as
small
as0
.02



through
the
circuit,
suchasby
operating
the
starter
motor
or
ohms
would
results
in
a
3
volt
drop
in
a
typical
150



turning
onthe
headlights
.
A
digital
multimeter
should
beused
amp
starter
circuit
.
(150
amps
x
0
.02
ohms
=3
volts)
.



lo
ensure
accurate
readings
.

"
Keep
in
mind
that
voltage
with
the
key
on
and
voltage
with
the
engine
running
arenotthe
same
.
With
the
ig-



1
.
Connect
digital
multimeter
positive
lead
to
positive
(+)
nition
on
and
the
engine
off
(battery
voltage),
voltage



battery
terminalor
a
positive
power
supply
close
lo
bat
should
be
approximately
12
.6volts
.
With
the
engine



tery
source
.
running
(charging
voltage),
voltage
should
be
approx-
imately
14
.0
volts
.
Measure
voltage
at
the
battery
with



2
.
Connect
digital
multimeter
negativelead
to
other
end
of
the
ignition
on
and
then
with
the
engine
running
to
get



cable
orswitch
being
tested
.
See
Fig
.
2
.
exact
measurements
.

3
.
With
power
on
and
circuit
working,
meter
shows
volt-
age
drop
(difference
between
two
points)
.
This
value
should
not
exceed
1
volt
.