BMW 1989-1995 525i Service Manual page 19

FUNDAMENTALS FOR THE DO-iT-YOURSELF OWNER
010-11
Volt-Ohm Meter (VOM) or Multimeter
Many of the electrical tests in this manual call for the mea-
surement of resistance (ohms) or voltage values. For safe and
accurate tests of ignition. fuel injection, and emiss ion control
systems . the multimeter, shown in Fig. 16. shou ld be digital,
with high (at least 10,000 ohms) input impedance. Some
meters have automotive functions such as dwe ll and pulse
width that are usefu l for troubleshooting ignition and fuel injec -
tion problems.
II
I
c.fil]
,
-
0
.
~
0
J:.~
.. . . .
.
? -
On --
'dO '.
B0 19FNG
B0 19FNG
Fig. 16. Multimeter or Digital Volt/Ohmmeter (DVOM).
CAUTlON-
The DME system. central body electronics. and
otner electronic systems may be damaged by the
high current draw of
a
test light with
a
normal in-
candescent bulb. As
a
general rule. use
a
high
im-
pedance digital muJrimeteror an LED test light for
all electrical
testing .
BMW Special Tools
Some of the more challenging repairs covered in this manual
call for the use of BMW special tools. This, however, does not
automatically mean that the job is too complicated or out of
reach of the novice.
Many of the BMW special tools mentioned in this manual are
simply the best thing to use to do the job correctly. In these cas-
es, the tool is identified with a BMW part number. See your au-
thorized BMW dealer parts department for information on how
to order special tools.
There are some jobs for which expensive special tools are
essential, and not a cost -effective purchase for one-time repair
by the do-it-yourself owner. This manual includes such repairs
for the benefit of those with the necessary experience and ac-
cess to tools. For the do -it-yourse lfer, the need for spec ial tools
is noted in the text, and whether or not BMW dealer service is
recommended.
EMERGENCIES
Changing a Tire
If
a tire goes flat while driving, pull well off the road. Changing
a tire on a busy street or highway is very dangerous.
If
neces-
sary . drive a short distance on the flat tire to ge t to a safe place.
It is much better to ruin a tire or rim than to risk being hit.
Stop the car on as flat a surface as possible, in a place where
you can be easily seen by other drivers . Avo id stopping just
over the crest of a hill. Turn on the emergency flashers , and set
out flares or emergency markers well behind the car. Passen-
gers should get out of the car and stand well away from the
road. Take the jack. tools, and spare wheel from the trunk.
Chock the whee l diagonally oppos ite to the one being changed.
Loosen the wheel bolts while the car is on the ground, but
leave them a little snug. Place the jack under the lifting point
nearest the wheel being changed (lifting points are shown in
Fig. 1). Use a board to provide a firm footing for the jack if the
ground is soft. Raise the car only far enough so that the wheel is
off the ground, and then remove the wheel nuts and the whe el.
Install the spare wheel. Install the wheel nuts and tighten
them by hand. then lower the car. With all whee ls on the
ground, fully tighten the nuts in a crisscross pattern. Torque the
wheel nuts when installing the wheel. Check the inflation pres -
sure of the spare tire.
Tightening Torques
• Wheel bolts to
wheel hub 100 + 10 Nm (74
±
7 ft-Ib)
EMERGENCIES