Correct ammeter

[G3L1946]

Hi, just seeking clarification. I might need to replace the ammeter on my 1955 G3LS ( it’s a bit suspect, needs testing ).It’s a Lucas 12-0-12 range but exact model not known. I see that the correct one should be , by the Lucas applications manual , a 36084F. The Matchless spares manual ( 1955 ) shows a 36084. Am I correct that a 8-0-8 should be fitted for a 6 volt system with a 12-0-12 being for a 12 volt system? Does the suffix F have any implication. I’ve retained the 6 volt system. Might as well get the correct one if mine needs replacing. I’m sure it being a 12-0-12 makes little difference if mine proves to be O.K.?

Regards,

Steve

[Groily]

If yours works it makes no odds that it's 12-0-12 but they were fitted on 12v machines (mainly, anyway). Never quite understood why, as there are more amps floating around at 6v than there are at 12v, for similar loads. I have 'some and some' depending what was to hand - and my bikes are 12v.
Should be easy enough to test yours if you have abattery and a bulb. A 6v 36W bulb should show a 6 amp discharge, an 18W brake light a 3 amp discharge, etc. Half that if testing using a 12v bulb.
The terminal posts do need to not be wobbly though, and the needle needs to be attached and the glass ditto!
Dunno what the F means, but nothing very much I'm sure!

[G3L1946]

Hi Groily,
That was on my mind regarding why, 12-0-12 for 12v system, when I would have thought it should be the other way around.An ammeter is an ammeter so as long as the ranges are covered ? Only problem would be that if the scale was too large then small swings would be less noticeable. I’ll test as advised and, if necessary, replace with a 8-0-8. The F can remain a mystery!
Thanks,

Steve

[Groily]

On the 'small swings' point, I actually have one of mine wired in parallel with the 'A' (battery) lead - ie the ammeter has a short link wire directly between the 2 terminals.
This reduces the risk of circuit failure due to any potential problem with a dodgy terminal post - but also reduces the swing. I think in the old days, production racing types did similar. Not that I am one of them!
When you realise what you're looking at, it is fine. Very small deflection towards Plus when charging, a bigger Minus with halogen headlight on and engine stopped. But enough movement to see what's happening, and the needle is very stable.

Doesn't really matter what it actually reads after all, as long as it's in neutral to positive territory when running above tickover sorts of speeds with the headlight on. I've had it like that this past couple of winters. (Similar to using the red-green witness LEDs sold by folk like Paul Goff in fact.)

For me, anything that might eliminate possible points of failure with these old 'lectrics is worth a go, as it's very darn dark in western France before about 8.45am this time of year, and I'm often out by 07.00 hours!

[G3L1946]

Hi Groily,
Thanks for info and your wiring solutions. The ammeter, when not under ‘load’,roughly sits on about -2 amps. When headlights go on ( main beam with rear light) reading of about -7 amps. Include the brake light and it’s about the same! It’s working I guess but not very accurately.
Can’t test when engine running as still setting up timing and points. It’s pretty dark most of the time in North Yorkshire!

Regards,

Steve

[Groily]

Typical Steve to have an off centre needle! I have one that's 1 amp + at rest and it is annoying (and not that easy to correct).
Your brake light is probably wired straight off the battery so won't register on the ammeter as a discharge, but you would see a charge when you apply the brake with the engine running when you get there. (Because the regulator senses the battery drain and tells the dynamo to compensate, then countermands the instruction when the load goes off again.)
Dark in N Yorks? I'd never have guessed! Freezing fog here all day just about, but at least we have daylight until 6pm by the end of Jan, to offset the late start in the morning. We are in the wrong time zone - should be on UK and Portuguese time really, apart from the confusion it would cause!

[G3L1946]

Hi Groily,

Lived in Spain for a while and found the time difference between U.K. and us a bit strange. After all, roughly on the same longitude ( Greenwich meridian, 0 degrees, runs through Alicante Province ). I was told it was due to certain 1930’s agreements between Germany and Spain! ( taken in context with the political climate at the time ). Just never got altered back again! I suppose it makes sense for EU purposes?

All the best,

Steve

[G3L1946]

Hi, The mystery of the F still remains. However, the attached is, supposedly, the correct one for the ‘55. CZU27 model ( 36084F).

Steve

[Groily]

Ha! You have been digging Steve. That is the one yes, according to all the various Lucas blurb. F must be for 'Funnily enough, no numbers on the dial'. Or 'Faintly indicative' . . .!
(Good to know if you're going to turn into a concours judge one day!)

[G3L1946]

Hi, Groily,
There's probably a medical condition, from which I suffer, that makes me such a pain in the a***! ( according to my wife, does it really matter!). I like the possible F references and I’m sure there are many more, some of which, are probably unprintable!
Having found the answer, Mmmmm, what should I turn to next!
All the best,

Steve