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NN.4 HEADLAMPS
From Car No. 70222 Mk. VIII headlamps with sealed beam units (Part No. BHA4144) were fitted to
cars exported to U.S.A.
From Car No. 72040 cars exported to Sweden have special headlamps with asymmetrical left dip (Part
No. BMK391). These are interchangeable with earlier types in pairs only.
NN.5 LUCAS C4011 DYNAMO
A later type of dynamo with increased output, Lucas type C40/1, was introduced, complete with Lucar
connectors, modified Lucas type RB106/2 control box, and a new-type ignition coil bracket.
The modified control box must not be fitted with the earlier-type dynamo,
NN.6 DISMANTLING A C40/1 DYNAMO
The instructions for dismantling the dynamo are basically the same as those given in Section N.4. The
C40/1 dynamo has a windowless yoke and is therefore not fitted with a cover band.
Access to the brushes is obtained by removing the commutator end bracket.
Ambient temperature Open-circuit voltage
50° F. (10° C) 16.1 to 167 68°F. (20° C) 160 to 16-6 86° F (30° C) 159 to 165 104°F. (40° C) 158 to
164
An unsteady voltmeter reading may be due to dirty contacts, but if the reading is outside the
appropriate limits the regulator must be adjusted.
Switch off the engine, remove the control box cover, restart the engine, and run the dynamo at 3,000
RPM. Turn the regulator adjusting screw (1, Fig. NN.3) in a clockwise direction to raise the setting, or
in an anticlockwise direction to lower the setting.
NOTE: -The operations of checking and adjusting the regulator should be completed within 30
seconds, otherwise false readings and settings, due to the heating of the shunt coil, will be made.
After adjustment a further check of the setting should be made by switching off and restarting the
engine and then raising the dynamo speed to 3,000 RPM., when the open-circuit voltage must
conform to the figures stated.
Refit the control box cover and restore the original connections.
Cut-out adjustments
To check the voltage at which the cut-out operates remove the control box cover and connect the
voltmeter between terminals 'D' and 'E'.
Start the engine and slowly increase speed until the cut-out contacts are seen to close, noting the
voltage at which this occurs. It should be 12.7 to 13.3 volts.
An alternative method of determining the exact point of contact closure is to switch on an electrical
load, such as a pair of headlamps, when the instant of contact closure will be indicated by a slight flick
of the voltmeter pointer.
If the cut-out operates outside the above limits it will be necessary to adjust it to within the limits. To do
this turn the adjusting screw (2, Fig. NN.3) in a clockwise direction to raise the setting or in an anti-
clockwise direction to reduce the setting.
Turn the screw only a fraction of a turn at a time and test the setting after each adjustment by
increasing the engine speed from zero and noting the voltmeter reading at the instant of contact
closure.
NOTE. -Like the regulator, the setting of the cut-out must be carried out as quickly as possible to avoid
errors due to the heating of the shunt coil.
Having set the cut-in voltage correctly, the 'drop-off setting should now be checked, and adjusted if
necessary so that the instant of contact opening occurs between 85 and 11-0 volts.
To check the voltage at which the contacts open remove the control box cover, disconnect the cables
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