Saab 95 1967, Service Manual

Page: 221 / 610

Ital IIIU
General
Please note the following points before t
nator or parts thereof:
Diodes may only be tested with D.C. Volta
ing 24 V-
9'°an9 lamps (119Vor 220 V) may not be used
for insulation or short curcmt tests, if the diodes are in
the circuit.
The 80 V 40 W test voltage for the stator winding insula-
tion test may only be aPplled if the diodes are discon-
nected.
While the engine is running, battery terminals may not
be disconnected to check the charging current on the ve-
hicle.
Semi-conductors are extremely sensitive to heat. To pre-
vent excessive heat when soldering, use a pair of flat pliers
to hold the supply wire near the diode. (Use a hot iron
and be as quick as possible.) Any mechanical damage to
the diode connecting wires must be avoided, e.g. do not
bend or load the wire directly on the diode (breakage due
to vibration).
The battery must be switched off or disconnected before
any repair work commences on the alternator, either
while in the vehicle or on the test bench.
Only instruments having not more than 8 V power supply
may be used for measuring resistances on the assembled
alternator.
esting the alter-
985 not exceed.
Testing the alternator in test bench
On the test bench, the alternator must be driven with its
own pulley. All connections must be made with correct
size cable shoes, or on the regulator with spade terminals.
Do not improvise the battery connection.
A 12 V battery must be connected parallel to the alter-
nator before any testing commences except for the regu-
lating voltage test and the nominal voltage and speed tests.
The battery will act as a buffer and smooth off any Peak
voltages arising from switching on or off the load.
Peak voltages exceeding the maximum PermiSSib'e value
will damage the rectification effect of diodes. The maxr-
mum permissible peak voltage on silicon diodes is approx-
50 V.
Excitation
As Opposed to D.C. generators, alternato f a
s“exciting properties after long Storage- The"? 0”
rs can lose their
charge indicator light of 12 V and minimum 2 W must be
FOnnected between terminals 61 and 8+ according to wir-
"‘9 diagram. The pre-exciting current will then flow
through the charge indicator light, D+/61 on the alter-
nator, D+/61 on the regulator, the closed regulator con-
tacts and DP to the exciter coil fitted to the rotor. It is
most important that the charge indicator light bulb is
minimum 2 W. Self-exciting commences as soon as the
exciter diodes are conducting at about to 2 volts. From
there on, the voltage increases rapidly, the voltage differ-
ence on the charge indicator light bulb decreases, and the
bulb will go out as soon as battery voltage is achieved.
Mounting of the alternator
The shape of the alternator housing does not permit a per"
feet mounting on the V block of the test bench. Therefore,
a special mounting unit is available.
WAR N l NG
When testing the alternator it must be mounted in
its ordinary attachments. It must not be clamped
on to the test bench.
Testing
with regulator
Mount the regulator to the test bench. Connect the alter-
nator to the voltage regulator. Do not interchange connec-
tions! Connect the exciter current ammeter to terminal
DF on alternator. Switch on battery; switch on charge in-
dicator light. Connect voltmeter to terminal B+. To pre—
excite the alternator, increase the speed from zero until
the output voltage is approx. 14 V and decrease speed
again.
let trim O tills man far en generatorspanning pa ca 14 V
och sedan sanks varvtalet ater.
Testing the regulating voltage at half exciter current
Connect voltmeter to terminal D+/61.
Run the still excited alternator without load and without
battery. Increase speed until exciter current falls to half
its maximum value. Check the voltage. Regulating voltage
13.5 to 14.2 V (68°F = 20°C).
Testing the nominal voltage speed
Connect Voltmeter to 3+. The alternator should also run
without load and without battery. Adjust the speed until
the output voltage is exactly 12 V. Check with tachome-
ter.
Nominal voltage speed 800—900 r/min.
m 321*5