25-09-2024, 08:47 AM
Hi Erich
Austin used "Three Brush" type dynamos for the Seven - these require a cut-out like the CF1 which isolates the dynamo below a certain threshold voltage e.g. about 7 volts for a 6 volt system. The cut-out is just that, there is no current or voltage regulation function in it, the three brush dynamo takes care of its own regulation (sort of !).
Morris used a "Two Brush" Lucas C39 Dynamo for the postwar Minor MM. This would be accompanied by a combined cut-out and voltage regulator designed for 12 volts
If your present dynamo was originally a 6 volt "Three Brush" type but has been converted to 12 volt two brush operation, it could in theory be restored to original spec if you can find any missing parts. The CF1 cutout could be rewound to operate at 12 volts, or a 30 ohm resistor added in series with its coil. Alternatively you could go back to 6 volts and change the battery, all the bulbs and the coil. Often items like the starter motor and horn are not changed when going to 12 volts, but you would need to check. Without knowing exactly what's been done and what your priorities are it's hard to advise in more detail.
I think if it were me I would leave things alone. Even Austin afficionados are often hard pressed to distinguish the minutiae of electrical systems !
Austin used "Three Brush" type dynamos for the Seven - these require a cut-out like the CF1 which isolates the dynamo below a certain threshold voltage e.g. about 7 volts for a 6 volt system. The cut-out is just that, there is no current or voltage regulation function in it, the three brush dynamo takes care of its own regulation (sort of !).
Morris used a "Two Brush" Lucas C39 Dynamo for the postwar Minor MM. This would be accompanied by a combined cut-out and voltage regulator designed for 12 volts
If your present dynamo was originally a 6 volt "Three Brush" type but has been converted to 12 volt two brush operation, it could in theory be restored to original spec if you can find any missing parts. The CF1 cutout could be rewound to operate at 12 volts, or a 30 ohm resistor added in series with its coil. Alternatively you could go back to 6 volts and change the battery, all the bulbs and the coil. Often items like the starter motor and horn are not changed when going to 12 volts, but you would need to check. Without knowing exactly what's been done and what your priorities are it's hard to advise in more detail.
I think if it were me I would leave things alone. Even Austin afficionados are often hard pressed to distinguish the minutiae of electrical systems !