Cambridge

[mike]

Hi a simple question, is the ignition warning lamp a screw in bulb or bayonet, a screw in came out but new one doesn' t seem to want to screw in . Tried by shinng a torch but could not make out which fitment it is, spring in the way.

[Rod]

Hi Mike,
I'm assuming you're still running the OE Lucas #318522 warning lamp with the 2.5V C252A 'flashlamp' globe?
If you are, the globe just sits there and is retained against the spring by the red lens (there might have once been a fibre tab around the globe to extract it).
Edit: or WL3 warning lamp, there's been some discussion about them earlier on this site.

[mike]

Found out there is no connections or wiring going to the light, no wonder it would not work will be looking for another unit, but not possibly of same design. Is it correct when wiring, one wire comes from ignition switch and other to 'd' terminal does that mean 'd' terminal on the ammeter will do, Thanks

[Rod]

'D' terminal on Control Box, Mike.
The light is intended (amongst other things) to indicate the voltage difference between generator output voltage and the system voltage downstream of the voltage regulator.
Any two-pole warning light assembly will do if you're not worried about originality. the extras on the OE Lucas one are there so a 2.5v globe can be used. Late-model generator systems generally used a 12v /6v 2.2W globe.

[mike]

Many thans Rod for the quick reply, 'D' on the control box it will have to be. Mike

[Rod]

Late edit: Forgot to say, if you're running an OE constant-current 3rd brush system, along with an 'IG' terminal, you should find a handy 'D' terminal on the block on the back of the ignition/lighting/charging control switch which might make it easier ('D' will already have one wire on it).

[mike]

Will have to look it is a 1937 Cambridge, don't know if it is 2 brush or 3.Mike

[peter_winney]

All Cambridge are 2- brush with voltage regulator (in control box). 3-brush went out sometime in 1934 with the 10. D on the control box is correct, the other connection being Ign on the back of the switch

[mike]

Thanks for all the valuable info, First I will look and see if there is any wiring remaining, had a cursory very gentle tug to see if any wiring was loose. none, so will have to get on my back to have a good look, not easy at 81 yrs old. Mike

[Rod]

Haha, yep can relate.
Might I suggest you start under the bonnet and make sure there are actually two wires on the 'D' terminal of the regulator first?
Then it should be reasonably easy to single out which one heads through the firewall and gently push-pull on that one with an observer inside the car (or your phone on video?) under the dash. It should be a plain yellow wire if your car is still wired to the Austin/Lucas scheme. The ignition wire (if you cant find the original off the back of the switch) can go to any ignition switched point that's conveniently located. The original colour would've been plain white for this one. However, my experience with fabric covered pre-war wiring is that the majority of the wires end up dirt coloured.
Good Luck!