Rolls-Rovce Silver Shadow
8
Bentley
T
Series
Workshop
Manual
Chapter
M
4.
Remove the glass paper and clean away all
Contact points-TO examine
abrasive dust and carbon.
5.
Assemble the generator by reversing the
pro-
1.
R.emove the two screws securing the control
cedure given for dismantling. Fit the brushes within
box cover
in-position; remove the cover.
their respective boxes to their original
'
bedding-in'
2.
Examine the contact points for oxidization,
positions.
burning, pitting and poor surface finish.
If any of
6.
The generator should be 'motored' for fifteen
these defects are found, the contacts should be
minutes by connecting the positive terminal of a
cleaned as described in Contact points
-
To clean.
12 Volt battery to the terminal marked
'D',
the
negative battery terminal to earth on the generator
casing and the field terminal of the generator to a
6
Volt supply. This 'motoring' is essential to
prevent any brush or commutator burning during
service.
Generator--To fit
Reverse the procedure given for removal, noting the
following points.
1.
Ensure that all the electrical contacts are
clean and secure.
2.
Fit the distance pieces in the correct position
to maintain alignment between the engine and
generator pulleys.
Misalignment will cause premature wear of
the driving belts.
3.
Check the tension of each driving belt as
described in Chapter
L
-
Cooling System.
Generator Control Box
Control box-To check
If
the control bcx is suspected of being faulty, carry
out the following tests and checks before fitting a
replacement unit.
General checks
Check if the battery is faulty by substituting a
battery known to be in good condition or by using a
hydrometer and a 150 amp heavy discharge tester.
1.
Check the tension of the generator driving belts
(see
Chapter
L
-
Cooling
System).
2.
Check the generator output as follows;
disconnect the cables from the generator terminals,
then, using a 'jumper lead', link the large
generator terminal marked
'
D'
to the small terminal
marked
'
F'.
3.
Connect a voltmeter between the link and earth,
and run the generator up to approximately
1000 r.p.m.;
if the voltmeter indicates a rising voltage then the
generator is functioning correctly.
4.
Examine the condition of the wiring in the
charging circuit and carry out continuity tests
between the generator, control box and ammeter.
5.
Check all earth connections, including the
control box.
Contact points-To clean
1.
To clean the contacts of the voltage or current
regulator, use a fine carborundum stone or silicon
carbide paper followed by methylated spirits (de-
natured alcohol).
2.
To clean the cut-out relay contacts, use a
strip of fine glass paper; do not use a carborundum
stone or emery cloth.
If the contacts are satisfactory, adjust the
voltage regulator as described in Voltage regulator
-
To adjust.
Voltage regulator-To adjust
Checking and adjusting should be completed as
rapidly as possible to avoid errors due to heating of
the operating coil.
I.
Withdraw the cables from the control box
terminal blades marked
'By.
Alternatively, insert a
strip of paper between the cut-out contacts as shown
in Figure
M44.
2.
Connect a first grade Zero to 20 Volt moving
coil voltmeter between the control box terminal
marked
'
D'
and a good earthing point.
Note
A convenient method of making this
connection is to withdraw the feed for
the ignition warning lamp from control
box terminal
'
WL', then clip the volt-
meter positive lead to the small terminal
blade thus exposed; this blade being
electrically common with terminal
'D'.
3.
Start the engine and run the generator at
1500
r.p.m.
4.
Observe the voltmeter pointer.
The voltmeter reading should be steady and read
-
between the appropriate limits given in Chapter A
-
General Information, according to the ambient
temperature. An unsteady reading may be due to
dirty contacts.
If
the reading is steady but occurs
outside the appropriate limits, an adjustment should
be made as follows.
5.
If the control box cover has not already been
removed, stop the engine; remove the cover by
removing the securing setscrews.
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