BMW 1989-1995 525i Service Manual page 165

BATIERY, S TARTER , A LTERNATOR
121 -3
NOTE -
On cars with automatic transmission.
a
starter relay
and
a
neutral safely switct: is used to prevent the en-
gine from starting in gear positions other than park or
neutrat. II voltage is not present at termina l 50 with the
key in the start position. check these components.
Fi g. 2. Starter wiring terrmnal ideruihcation,
If the solenoid audibly clicks but the m010r does not turn.
switch on the lights and turn the key to the start position. If the
lights go out while starting. the starter may have a short circuit.
If the lights stay
on. the solenoid is most likely the cause of the
fault.
If the starter turns the engine slowly, chec k the wires. termi-
nals and ground connections of the batte ry and starter for
good contact. If no faults can be found, the starter may be
worn and should be replaced.
BATIERY CHARGING
Discharged batteries can be recharged using a battery
charger. Prolonged charging causes gassing that will evapo-
rate the electrolyte to a level that can damage the battery. It is
best to use a low-current charger (6 amp or less) to prevent
battery damage caused by overheating.
WARNING -
The gasses given off by the battery during charging
are explosive. Do not smoke. Keep open /lames
away from the lap of the battery, and prevent elec-
trical sparks by turning off the battery cha rger be-
fore connecting or disconnecting it.
CAUTION -
o
Electrotyte can damage the car. II electrolyte is
spilled. clean the area with
a
solution of baking
soda and water.
o
Atways allow
a
frozen battery to thaw before at-
tempting to recharge
it.
o
Always disconnect both battery cables during
battery charging. This will prevent damage to the
alterna tor and any solid-state components. Do
not exceed t6.5 votts at the battery.
ALTERNATOR SERVICE
Before checking the alternator and regulator. make sure the
battery is fully charged and capable of holding a charge.
Check that the battery terminals are clean and light and the al-
ternator drive belt is properly tensioned and not severely
worn.
To check charging system
1. Turn ignition key on. Check that the charge warning
lamp comes on.
NOTE -
II the warning light does not come on. repair any wiring
or bulb faults before continuing to check the charging
system.
2. Remove the terminal cover from the rear of alternator.
3. Check for battery voltage between ground and terminal
8+ at back of alternator. Then turn ignition on and
check for battery voltage between terminal 0 + and
ground.
If
voltage is not present at either point, check
for wiring for faults. See Fig. 3.
NOTE-
Terminal B+ is supplied battery voltage directly from the
battery. Terminal 0+ is supplied battery voltage via the
charge warning bulb when the key is on or the engine
is
running.
4. If no faults are found up to this point. test alternator out-
put.
5. If a load tester is not available, a crude output test can
be done by running engine at about 2000 rpm and turn-
ing on electrical loads (fans. lights and rear window de-
froster. wipers). When fully loaded, battery voltage
should be at least 12.0 VDC.
ALTERNA TOR SERVICE