Ignition Coil

technical data -

Lucas L.O. model B12 revision 0 (Lucas part number 45012A/D, later DLB101). Lucas service number 402033.

Primary resistance (approx.) 4Ω, secondary resistance (approx.) 6.6kΩ

Black painted, tinplate bodied coil - base is stamped with (eg.) ER12V 649 - where last digits represent month and year (June 1949 in this case).

The terminals are marked CB and SW for 'Contact Breaker' (Distributer) and (Ignition) 'SWitch'. The latter being the 'hot' side, or connection to the negative terminal of the battery.

maintenance -

Keep the unit clean, checking for loose or damaged wiring and replace leads if necessary.


problems -

Most likely mechanical damage due to carelessness. It is possible for the terminals to be snapped and for the bracket to break if mistreated.


removal -

Two bolts to left and right of the coil with spacers from engine block.


other notes -

Altho the later revision 1 coil can be substituted, it differs slightly in appearance.

The B12 was superceded by the aluminum bodied HA12 (Lucas part number 45075A/D). There was also a 45075E/F which appears to differ only in the addition of Lucar connectors.

The Remax, ES3 is also an interchangeable part.

If you have a ballast resistor coil, you only need to add the correct (high current) resistor, to be able to use it on the L.D.10.
To get the benefit of the low resistance coil on starting, fit a relay which will operate and close its contacts when the starter knob is pulled. Run one wire from each side of the ballast resistor to the relay contacts, so that the resistor shorts out through the relay whenever the starter motor is energised. The full battery voltage will then go to the low-voltage coil.
A low resistance coil should give an advantage for winter starting but for normal use, with a large battery in good condition, a relatively low compression engine and properly set up points, the improvement may not be noticeable.


None yet.