Page 1
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Alternator 321-1
Alternator
Principle'of operation . . . . , 321-1 exiense F.,...cee , Sete, 324-8
Internal circuitry <a ae 321-3 HGStIMeR xt te a een 324-9
Removal and refitting . .-. . . 4... 321-4 Checking and testing of
To dismantle 3 ate a) Wet Sees components ........., . 321-10
Toassemblo, 2) . . 321-6
When the engine is running. the alternator sup-
plies the various electrical components and also
charfes the battery.
The pulley is equipped with vanes to dissipate
the heat. generated jn the alternator, When the
pulley is rotating, the vanes draw airthrough the
alternator to provide the necessary cooling.
The alternator is mounted on the side of the en-
gine and driven by twin V-belts.
Two alternator models are in use, depending:on
the variant and market specification: The Boseh
70 A and 80 A.
Principle of operation : f
When the ignition is switched on, the circuit will
be closed from the ignition switch via the wam-
ing lamp to terminal D— on the alternator, Cur-
rent will then flow through the roter winding and
to earth through the voltage regulator,
Current flowing through the rotor generates: a
magnetic field around the rotor. When the en-
gine is Started and the rotor starts to rotate, the
magnetic field will also rotate, generating an al-
temating current in the stator windings. The al-
ternating current is rectified in the rectifier dio- z ere
des; and the direct currentwill be supplied to the SZ -
battery via terminal B+-. Bosch 80.A alternator
SAK
The current from the stator windings also flows
through the excitation diodes to the voltage re-
gulator, where it is used for-controlling the out
put voltage. When the voltage has risen to about
14 V or above, the regulator will reduce the cur
rent flowing through the rotor winding.
Saab 900
Page 2
321-2 Alternator
This weakens the magnetic field and thus re-
duces the current generated in the stator wind-
ings,
The voltage regulator thus limits the voltage to a
maximum of approximately 14 V
The warning lamp is also affected by the voltage
supplied by the stator windings via terminal D+
on the regulator, so that when the voltage on
both sides of the warning lamp is the same, the
lamp will not be alight: The lamp therefore indi-
cates whether the alternator is charging.
No current limiting relay is required, since the al-
ternator limits the current itself. When the alter-
nator is running at high speed, the frequency of
the induced alternating current will also be high,
and when the output current has reached a given
value, the resulting resistance (impedance) will
be of such magnitude that any further current in-
crease would be impossible.
Caution:
Never:
® earth the excitation terminals of the al-
tenator or regulator or the interconnect-
ing cable.
© reverse the polarity of the regulator.
® disconnect the regulator or battery whi-
le the alternator is running.
® remove the alternator while the battery
is connected,
* run the alternator if the cable between
the negative terminals of the alternator
and the regulator is not connected.
* test the alternator and regulator as
semblies in the car or on. a test bench
unless the battery is connected.
® reverse the polarity of the battery, as
this may result in serious damage to the
alternator.
Alternators should be overhauled only by
specialist workshops. It is vitally important
that they are dismantied and tested cor-
rectly, as seemingly minor errors may lead
to serious damage.
Caution:
To avoid damage to the alternator, discon-
nect the negative (-} battery cable and all
alternator connections before carrying out
any electric welding on the car.
Saab 900
Page 3
Alternator 321-3
Internal circuitry
Con- The alternator, which is internally ventilated, has
eal a 12-pole rotor and six silicon diodes for rectifi-
Out cation. The 80 A alternator has 12 silicon diodes
for rectification and an additional two for the
“third circuit”.
An excitation diode is connected to each of the
three stator windings. The excitation diodes are:
interconnected at terminal D+. The stator wind-
ings form three phases. Those of the Bosch 80 A
are star-connected, and those of the Bosch 70 A
are delta-connected,
The six (14 on the 80 A) rectifier diodes are con-
nected in the form of a bridge circuit, |e. three
‘seven on the 80 A) diodes are connected for nor-
mal polarity (anode to the terminal) and three
(seven or the 80 A) for reversed polarity (anode
to earth).
The diode holder js either insulated from the sta-
tor frame (earth) or directly earthed, according to
the polarity. The excitation winding is mounted in
the roter, which has claw-type poles, with alter-
nate claws acting as north pole and south pole.
The excitation current |s supplied to the rotor coil
via slip rings on the rotor.
Swab 300
Page 4
Lj
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F
e
Alternator 321-5
To dismantle
The Bosch 70 A and 80 A alternators
Drive end bracket
Stator
Slip-ring end bracket
Rotor5 Rectifier unit
Voltage regulator and brush-holders
Pulley
Large thrust washer (80 A only)
Interference suppressor (capacitor) (80 A only)
OBNDEWNHP
1 Clamp the pulley and remove the pulley nut,
using a 22 mm socket. Remove the pulley
and fan.
2 Remove the voltage regulator from the alter-
nator,
Voltage regulator removed from alternator
Saab 900
Page 5
321-6 Alternator
3 Separate the stator and slip-ring end
bracket from the drive end bracket and rotor.
Mark the position of the drive end relative to
the stator ring and slip-ring end bracket.
4 Remove the retaining screws and nut for the
rectifier unit, and separate the stator and
the rectifier unit from the slip-ring end
bracket.
5 Unsolder the stator leads from the rectifier
unit.
6 Place the drive end bracket on a suitable sur-
face and press the rotor out carefully. The
bearing can now be dismantled. To avoid da-
mage, prevent the rotor from falling as it
comes free of the bracket.
7 Use an extractor to remove the bal! bearing
at the slip-ring end.
To assemble
4 Pack the bearings with Bosch Ftiv34
grease. Press the ball bearing into the drive
end bracket with the enclosed side facing
the drive.
aE
2 Press the drive end bracket onto the rotor.
3 Press the ball bearing onto the slip-ring end
of the rotor, with the enclosed side facing
the slip rings (see illustration).
4 Solder the stator leads to the rectifier unit.
5 Fit the rectifier unit to the slip-ring end brac-
ket.
Saab 900
Page 6
a
| @ Alternator 321-7
6 Place the snap ring for the bearing in the
i slip-ring end bracket, and refit the drive end
bracket and rotor to the slip-ring end bracket
and stator, as described earlier,
7 Check the length of the brushes. With the
brush-holder removed, the brushes should
project at least 5mm (0.2 in) from the brush-
holder. Refit the brush-holder,
8 Fit the fan and pulley. Make sure that the wa-
shers are fitted in the correct order (see illu-
stration). Tighten the nut to a torque of 34 -
39 Nm (25 - 29 Ibf ft).
(If the fan has done more than 100000 km
(60000 miles) at the time of overhaul, it should
be replaced.)
ie =]
Saab 900
Page 7
Alternator 321-13
D. To check the brush-holder and con-:
nections (brush-holder or rotor removed)
1 Check that the brushes mave freely in the
holder.
2? Check the wear on the brushes. The brushes
should project at least 5 mm (0.2 in} from
the holder when the holder is fitted.
3 Check that the brushes are well insulated
from each other. Measure the resistance
between the brushes.
4 Check that the contact between each brush
and the "-" or BF terminal is good.
E. Insulation test on assembled alterna-
tor
After the alternator has been dismantled and re-
assembied, check the insulation between termi-
nal B+ and earth by means of an insulation
lester
Fault-tracing
Alternator not charging
Possible causes:
a Alternator drive belt siack
b Charging circuit-and/or earth circuit open
¢ Brushes defective
d Short-circuit in diode
e Excitation circuit open
T Voltage regulator defective
g Rotor winding open
h Stator earthing
| Earth corinection of excitation diode unit open
or short-circuited
insufficient or irregular output current
Possible Causes:
a Alternator drive belt slack
b Irregular breaking in-charging circuit
c Brushes worm
d Voltage regulator defective
e Rectifier diode open or short-circuited
f Rotor partially short-circuited
8 Stator connection to earth broken or partially
short-circuited
Current too high
Possible causes:
a Voltage reguiator defective
b' Poor contact between regulator and alternator
Alternator noisy
Possible causes:
a Alternator drive belt very worn
b Pulley incorrectly fitted
¢ Alternator and crankshaft pulleys misaligned
d Bearings worn or defective
e Rectifier diode short-circuited
f Alternator mountings loose
Saab S00
Page 8
340-2 Ignition system
Note:
The Hall sensor and the rotor cannot be removed
separately. If the sensor unit is suspected of
being defective, the entire distributor must be
replaced.
Charging the ignition coil
The slotted rotor breaks the magnetic field. No
voltage is generated in the Hall sensor. The
amplifier is energised, the primary circuit is
closed and the primary winding charges the igni-
tion coil.
Firing instant
The slot in the rotor is in line with the Hall sensor.
The voltage generated in the sensor is sensed by
the amplifier, which breaks the primary circuit.
The spark-firing voltage is now induced in the
secondary winding of the coil.
Amplifier
The amplifier is mounted on a cooling plate, for-
ward of the left-hand wheel housing.
The amplifier amplifies and converts the pulse
from the distributor. The amplified and con-
verted pulse is then used to contro! the charging
and discharging of the coil.
The amplifier also monitors and controls the
dwell angle.
The use of hybrid technology in the design of the
module has made it possible to produce an ex-
tremely compact amplifier.
reiterate
pi
4 Slotted rotor
2 Hall sensor
1 Slotted rotor
2 Hall sensor
3 Amplifier
4 |gnition coil
Saab 900
Page 9
SCM et ae cere ean = ew hw!
Fault-tracing chart
Conditions for testing
Battery fully-charged, fuel in tank, engine and
ambient temperatures 32 - 104°F (0 - 40°C}_ (The
temperature has @ considerabie effect on the
values recorded.)
The starter motor turns,
but the engine does not
fire or starts but has poor
Grivability.
Y=
sane
Check the spark at a gap of
12mm."
Ignition spark at 12 mm?*
=
y=
Check the ignition timing.
ts the ignition timing cor-
Check the HT part of igni-
tion system: Spark plugs,
distributor arm, distributor
Cap, HT leads and connec-
tions.
Ignition spark at 12 mm?*
Adjust the ignition tim-
Se
ing.
rect?
\ a
Check the fuel system.
Is the fuel supply to the en-
gine sufficient?
no
> Repair the fuel system
S
Rotate the amplifier,
which turns on the earthed
bolt, So that the plug on
the side is visible. Pull
back the rubber dust cover
on the amplifier plug, but
don't disconnect the plug.
Connect a voltmeter be-
tween terminals 4 and 2,
Switch on the ignition and
measure the voltage,
which should be the same
as the battery voltage.
Correct voltage reading?
Rotate the amplifier and
pull back the rubber dust
cover from the plug, but
don't disconnect the plug.
Connect a voltmeter be-
tween terminals 4 and 2
and measure the voltage,
which should be the same
as the battery voltage,
Correct voltage reading?
Check the wiring from
the ignition switch to
the amplifier
Rectify the fault.
+
Check the wiring from
the ignition switch to
the amplifier,
LS
Rectify the fault
Disconnect the connector
from the distributor, Mea-
sure the voltage between
terminals "+" and "-". It
should be the same as the
battery voltage.
Correct voltage reading?
First determine
whether the wiring be-
tween the amplifier and
the distributor is in
good condition. If it is,
fit a new amplifier.
no
v yes
v”
Check the ignition coil re-
sistance. Primary winding
(15 and 1): 0.52 - 0.76
ohm. Secondary winding
(4 and 1): 7.2-8.2 kohm,
Correct resistance read-
no
Fit a new ignition coil.
i
ings?
v
Disconnect the connector
from the distributor. Con-
nect a voltmeter between
coil terminalis 15 and 1.
Switch on the ignition. The
voltage reading should
drop from about 6 V to OV
in 1-2 seconds.
Correct voltage reading?
Connect a voltmeter be-
tween terminals 6 and 3 of
the amplifier, but don't re-
move the plug. Remove
the distributor cap and
dust cover, Run the starter
motor briefly until the slot
of the slotted rotor is in the
air gap at the Hall sensor
Leave the ignition
switched on. The voltage
reading should be 0.4 V or
less,
Correct voltage reading?
no
*
Hall sensor faulty. A
new distributor must be
fitted.
,
no
i Fit a new amplifier |
Repeat the above until the
slotted rotor closes the
gap at the Hal! sensor. The
voltage reading should
now be 5.0 V of more.
Correct voltage reading?
Hall sensor faulty. A
new distributor must be
fitted.
ce
S
The engine should now
Start
yes
Concerns the special spark tester. When
checking with a separate spark plug, the elec-
trode gap should be about 4 mm (0.16 in).
Page 10
340-18 Ignition system
Caution
Remember to check that the car is in neut-
ral before switching on the starter motor.
When the engine is being run by means of the
TSI, the ignition switch is by-passed, and the
radiator fan will therefore not run. So if the en-
gine is run for more than about ten minutes, the
ignition system should be switched on by means
of the ignition switch, to enable the fan to run.
This is necessary because if the engine runs too
hot, a faulty reading of the CO content in the
exhaust is likely to be obtained.
Note:
Bear in mind that when the ignition is switched
on, all other electrical components connected
across the ignition switch will also be switched
on.
Checking and adjusting the timing
4 Connect the timing service instrument (TSI)
or equivalent equipment.
2 Disconnect the vacuum hose from the throt-
tle housing or carbuetter.
3 Start the engine and run it as specified in
section 023, "Technical data”.
4 Check the timing and adjust as necessary.
Location of HT leads
bistaLitea ELeRLPE REET TS |
- 8-valve model
Saab 900