Ignition warning light

[Tony Fearn]

I have a couple of spare pre-war ignition warning lights (early thirties) which fit into the instrument panel on the dashboard. I think they should have the very fine resistance wire wound around the outside like the one on my 1934 Short Saloon.

I need to use one of them on the "Flying Fox" I am resurrecting, but neither of them have the wire coiled around the outside. Will this make a difference? JCSpares don't have a complete one either.

The theory behind the resistance wiring was explained to me this afternoon at the Ex-Employees meet at Bradford Industrial Museum, and it seems as though it is a necessary item.

Has anyone any experience of using an ign. warning light without the windings on a pre-war?

Tony.

[Tony Fearn]

Thanks Pat.

Will do tomorrow, but it will have to go into the Gallery as I don't know how to post photos on these threads.

I am very envious of Leo's prowess and super sharp images.

Tony.

[Tony Fearn]

Hello again Pat.

Sorry it's a bit late but I've posted three pix on my album in the Gallery under - "Ignition warning light"

Front of panel showing chromed front bezel.

Close-up of another unit which shows some of the remaining resistance wire wrapped around the exterior of the barrel, this should be end to end and soldered into contacts at the terminal end. This is the type I need, and apparently the wire coils on the outside are very necessary. You will also see that the chrome bezel screws into the front of the unit.

The back of the ignition light seen on the panel. As you can see there is no external wiring.

Tony.

[Bryan Walker]

Hi Tony,
The ignition warning light socket with the series reistance wire wrapped around the body is designed for 2.5Volt tourch bulbs (0.2A), (when 2 resistors are in series they have the same current running thru them but the voltage is sheared ie the resistor drops the voltage down for the bulb.
The later warning lights used standard 12v bulbs with no series resistance.

I hopethis helps

Bryan

[ian Howell]

I hope this might help . .

Presumably the use of a 2.5 volt 0.2 watt bulb is to minimise the heat generated IN the lampholder, with the surplus energy being dissipated by the BODY of the bulb holder.

In any event, IF the purpose of the external windings is to reduce the car's 12V supply to 2.5V, then a suitable series resistor would do the job.

What is suitable?

Well the idea is to 'drop' about 10V across the resistor, and with the current for the SERIES lamp being 0.2 Amps, this gives a resistance of (10 / 0.2) = 50 Ohms.

But there could be a problem with the surplus energy.

The resistor needs to dissipate (10 x 0.2) Watts = 2 Watts and this could get fairly warm.

So, if you ask the local electronics supermarket for a 2 (or more) Watt 50 Ohm resistor, you should be OK. Then you need to wire it in SERIES with the 2.5 volt bulb in the holder - but somewhere where the heat will not do any damage.

I will need to think a bit more, but it shold be possible to use a standard 12 volt bulb in series instead of the resistor.

More to follow?

[Tony Fearn]

Hi Bryan and Ian.

Thanks for the replies. I have found another ignition warning light in my "electrics tub" which may be from a later pre-war, or even a Bradford which seems that it has never had a wire wrapped around the barrel, so Ian's last sentence might be true. At the moment I won't use this as it's not quite the same pattern as the 1934 type.

Yesterday I finished wiring the 'Fox' and everything seems to work. The ignition light (without the resistance wiring) lights up, but as the engine hasn't been started yet, I don't know the state of the dynamo or whether the light will go out as it should.

The warning light is wired as per the 1933/34 diagram in my album on Jowetttalk, between +D and IG on the PLC switch. I suppose this is in series.

The actual key-mediated ignition switch is a bit hit or miss - I'll bet if I went over a big bump in the road it might switch itself off at 30mph - so I've added a flick switch across the terminals to make sure this doesn't happen.

Tony.

[ian Howell]

Tony: -

Is this what you need? On eBay 130153974172

[Tony Fearn]

Thanks for the eBay link Ian.

I'll leave the wiring as it is for the moment as I know for sure that the ignition switch I've added works ok.

The eBay switch is for a later Jowett.

Regards,

Tony.

[AlanBartlett]

What is the funtion of the light?, As I seem to have gathered, when you turn on the iginiton key, the light pops on, then once you start the engine and is running it goes out, what would cause the light to remain on a low ilumination when the engine is running?

[Forumadmin]

It remains on because the voltage of the battery is higher than the voltage of the dynamo. This normally indicates a faulty dynamo or regulator. May be able to cure by adjusting voltage regulator.

[AlanBartlett]

So possibly an over charged battery?

[george garside]

[quote="Forumadmin"]It remains on because the voltage of the battery is higher than the voltage of the dynamo. This normally indicates a faulty dynamo or regulator. May be able to cure by adjusting voltage regulator.[/quote]

pre war twins should have 3rd brush dynamo rather than a regulator and some degree of regulation using summer or winter ( roughly half or full)charge setting on lighting switch. given low dyno output & heavier use of electicity than when car was made - more lights, indicators etc it is probably sensible to just leave it on winter charge setting unless on very long daylight run.
george

[Forumadmin]

Thanks George for putting us moderns straight.

You can also get that sort of fault using an electric fan (or other appliance) that is connected the wrong side of the regulation circuit which measures the amps taken. That is for example, if you connect the fan to the same place as the horns.

A check with the voltmeter should prove it. You should have 13,8 v at the battery with appliances switched on or off at about 2000rpm.