Electrical system on Ulster Rep

[Erich]

Hi All,

Electrical issues are a bit of a mystery for me. First off, my Ulster Rep came with a Morris Minor(postwar) cut out and a 12 volt system. I subsequently got a CF-1(its a 1930 SWB chassis). They CF-1 is missing its metal fuse strip. Are these available?

My second question involves the CF-1 capacity. As it is 6 volt cut out, do I have to convert back to a 6 volt system, or can it be used with a 12 volt system? If the former, I will need to have the dynamo converted to three brush presumably, as well as change the battery and the light bulbs. Will the coil need to be changed as well? Anything else?

Thank you in advance for any help.

Erich in Mukilteo

[John Cornforth]

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 !

[Dave Mann]

Here's a 30 ohm resistor fitted in the base of a 6 volt CF1 to make it suitable for 12 volts.    

[Erich]

Thank you Dave and John. This definitely gives me things to ponder. Do either of you have any sources for the metal fuse strip on the CF-1?

Erich in Mukilteo

[David Cochrane]

I've never seen any - I would just use ordinary fuse wire of the correct grade (5A?).

[Tony Press]

I've never seen any - I would just use ordinary fuse wire of the correct grade (5A?).

My 29 Saloon still has two original light metal strips- very delicate !

The other two cars use house fuse wire (I think 3 amp) as David suggests

[Peter Naulls]

Unless originality is paramount I would leave it as it is. My special has a 12 volt conversion with Morris Minor regulator and it works very well indeed.

[Charles P]

Unless originality is paramount I would leave it as it is. My special has a 12 volt conversion with Morris Minor regulator and it works very well indeed.

Quite. It’s easy to wire a Morris Minor RB106 to work as just a cutout.

I have a DVR3 electronic regulator hidden in mine with a DFL dynamo and the field coils rewound for 12v