Cambridge

[mike]

Many thanks to everyone for great information, the only thing I now need to know,is if I cannot find any wires there, does the new wire need a specific rating. Thanks p.s going to run with 12v bulb

[peter_winney]

Many thanks to everyone for great information, the only thing I now need to know,is if I cannot find any wires there, does the new wire need a specific rating. Thanks

If it is the D wire I think the short answer is "beefy" as it takes the charge from the dynamo, but I don't know how to calculate ratings. The only rewiring I have ever done on a Ten I used wires stripped out of a 12 year old scrap car.

[Rod]

Peter & Mike:
No, the lamp is not part of the high-current circuit.
It illuminates in response to the difference in voltage between the car power supply network downstream of the voltage regulator and the output voltage of the generator upstream of the voltage regulator(i.e. B+ vs Vgen in modern terms)
The charging system will be functional even if the warning light circuit is fully open circuited, and some cars of the era, even with the latest tech of the day (the 2-brush CVC system!!), never had a lamp and relied on the operator eyeballing the ammeter.
Later ~50s/60s vehicles with generator systems typically use a 2.2W globe, which for a 12v system is 2.2/12 = ~ 0.18A so any 9/0.3 cable or 14/.012 cable (which is rated at 5.75A) will be well over-specc'd for this application.
Note, you need a 2-terminal socket* as unlike most warning lamps which sink battery voltage to earth, the globe filament has to be effectively across the output terminal of the generator and the output of the ignition switch.
Edit: *for instance Lucas SPB354 or similar. Your typical LED one most likely wont work (unless its non-polarised).

[mike]

Hi Rod by two terminal socket do you mean the warning light has to have two connectins one for ignition and the other for the D connection, this is the type I have ordered which takes a 12v bulb, does it matter which connection goes to which Thanks Mike

[Rod]

Hey Mike,
Yes, two connections. Two 1/4 inch Lucar( = spade) terminals or two screw terminals etc
It doesn't matter which way around you wire it.
All the Best,
Rod

[mike]

Thanks for all the info, now got it clear in my head what to do Cheers Mike

[mike]

Just a quick update hope I have done it correct. Took my live from the fuel gauge, tested which connection was the switched live by taking them off and using a test lamp. Wired up to the D connection on control box eureka, one working ignition warning lamp, started car and when revs increased just a little out it went, petrol gauge working too. I must thank everyone for their most valued help. Regards Mike Hobson

[Rod]

Good to hear, thanks for the feedback!