BMW 1989-1995 525i Service Manual page 376

600-2
ELECTRICAL SYSTEM-GENERAL
CAUTION-
o
Always turn off the engine and remove the neg-
alive (-) battery cable before removing any elec-
trical components.
o
Connect and disconnect ignition system wires.
multiple connectors. and ignition test equipment
leads only while the ignition is off.
o
Do not disconnect the battery with engine running.
o
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 least one minute before
boosting the battery
a
second time.
o
Do not use
a
test lamp that has
a
normal incan-
descent bulb to test circuits containing electronic
components. The high electrical consumption of
these test lamps may damage the components.
o
Many 01 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 .
o
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.
o
Always switch
a
test meter to the appropriate func-
tion and range before making test connections.
o
Do not try to start the engine of
a
car which has
been heated above 176'F (8Cl'C) . (for example.
in
a
paint drying booth) until allowing it to coof to
normal temperature.
o
Disconnect the battery before doing any electric
welding on the car.
o
Do not tow
a
car suspected of having
a
defective
ignition system without first disconnecting the ig -
nition control unit.
o
Do not wash the engine while it
is
running. or any -
time the ignition is switched on.
Electrical Test Equipment
Many of the electrical tests described in this manual call for
measuring voltage, current or resistance using a digital multi-
meter (DMM). Digital meters are preferred for precise mea-
surements and for electronics work because they are
generally more accurate than analog meters. The numerical
display is also less 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 other-
wise require a multimeter. The LED indicates when voltage is
present between any two test-points in a circuit.
WIRING DIAGRAMS
CAUTION-
o
Choose test equipment carefully. Use
a
meter
with at least 10 megohm input impedance. or an
LED test light. An analog meter (swing-needle)
or
a
test light with
a
normal incandescent bulb
may draw enough current to damage sensitive
electronic components.
o
An ohmmeter must not be used 10 measure resis-
tance on solid state components such
as
control
units or time delay relays.
o
Always disconnect the battery before making re-
sistance (ohm) measurements on the circuit.
WIRING DIAGRAMS
The wiring diagrams shown in Electrical Wiring Dia-
grams have been specially designed to enable quick and ef-
ficient diagnosis and troubleshooting of electrical
malfunctions.
Wiring Codes and Abbreviations
A tremendous amount of information is included in each
wiring diagram if you know how to read them. For example ,
you will notice that all electrical components. connectors, fus-
es, and ground locations are identified using a unique num-
ber. Each of these numbers corresponds to a particular part in
the circuit. A listing of these component numbers , their identi-
fications and locations is given in Electrical Wiring Dia-
grams.
Wire colors in the diagrams are abbreviated. Combined color
codes indicate a multi-colored wire. For example the code
BLU/RED indicates a Blue wire with a Red stripe. Wire color ab-
breviations are listed below.
NOTE-
Sometimes the color 01 an installed wire may be differ-
ent than the one on the wiring diagram . Don 't be con -
cerned. just be sure to confirm that the wire connects
to the proper terminals.
Wire color codes
BLU Blue
BRN Brown
YEL. Yellow
GRN Green
GRY Gray
ORG Orange
RED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Red
BLK Black
VIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Violet
WHT White