Fitting a Dynamator to a positive earth car

[Tony]

Hi All, Due to the reliability of the old type regulator ( my third one). I have decided to convert to a Dynamator to eliminate the regulator.
As part of the switch people seem to recommend that I also change the amp meter to a volt meter. This avoids heavy amps and cables running up through the old amp meter.

As my car is a positive earth car I have to order C42 Dynamator ( A C42 equivalent to my old C42 Dynamo).

I cannot convert to a negative earth as my electric power steering is a positive earth version.
On speaking to a guy who makes period style volt meters he states they will not work on a positive earth car ( or his will not) and I would need to stick with an amp meter.


Now the question is:-
How do I wire and amp meter to the Dynamator when the voltage regulator is redundant with a alternator conversion

[johnetype]

It is definitely a good idea to remove any ammeter when fitting a Dynamator but if you want to know were in the circuit to wire it in I'd ask Dynamator's advice.

Given being on -ve earth would make life easier in the future should you wish to fit more electronic devices, I'd contact the electric power steering supplier and see what's involved in returning it to it's native -ve earth first. That may be easier than you might imagine.

I could suggest how to change the polarity of the voltmeter but given they are a thermal device, I'm not convinced that they are polarity sensitive anyway. Someone else may know or I can check mine.

[Tony]

Hi John, thank you for the quick reply. Apparently I can buy a Nisanger volt meter from America but is is £110 .plus shipping. This seems a bit of an expensive way to go so if anybody knows a way around this it would be a great help.

Tony

[MSM]

Tony

Have a look at Holden.co.uk. They do Smiths/Lucas voltmeters which are cheaper than Nisonger.

And in reply to your first post I find it hard to believe that voltmeters are only negative earth. The Holden voltmeter has two separate insulated terminals.

Mike

[Tony]

i Mike, spoken to Holden (SNG) and yes they have a fully insulated Volt meter. It is a chrome bezel meter with Smiths not Lucas on it. I guess it is for a Series 2 E Type. With postage, vat etc it is circa £70. So not quite matching like a Nisonger but then again a 62 E Type never had a volt meter anyway, so is matching that important. It’s a case of pay my money and take my choice.

If I wanted to keep my amp meter does anybody know how it would be wired up. ?

Thanks Mike.

[johnetype]

I pulled my Series 2 original voltmeter and did some tests, from which I learnt:

Both supply terminals are insulated from the body.

The voltmeter isn't polarity sensitive, you can connect it up either way round and it still works and shows the correct voltage.

It consumes approx 0.1 amp in operation.

My car has a Smiths unit with a black bezel. There's a Lucas unit with a black bezel on eBay currently for £50.

These voltmeters were fitted across the Jaguar range "in the day" so a XJ6 or other would be a suitable source of supply.

I still wouldn't fit an ammeter with an alternator replacing a dynamo not least because you will struggle to find a new ammeter that can handle the increased current output, let alone the fire risk.

(I can't resize my photos below 256M to allow me to upload them)

[MSM]

Hi Tony

Wise words from John there -

I still wouldn't fit an ammeter with an alternator replacing a dynamo not least because you will struggle to find a new ammeter that can handle the increased current output, let alone the fire risk.

If you want to see how an ammeter is wired up look in the Knowledge Base at a wiring diagram for a Series 1. Because of what John says you need to remove your existing ammeter from circuit if you fit a dynamator.

The concensus of opinion seems to be that a voltmeter is a more useful instrument than an ammeter and it is simpler to install.

[Series1 Stu]

I agree that a voltmeter is probably more useful but if you want to keep an ammeter for authenticity reasons then you can. You can buy a 60 amp meter for not a lot of money and fit the internals into your existing housing. I did just that and it works well. I think I have photos of the process.

As an alternative, or a temporary workaround, you can park both ammeter wires on one of the main terminals.

Regards

[Tony]

Hi Stuart, that is an interesting concept of fitting a 60amp into my original amp meter. Any photos or diagrammed would be appreciated.

Tony.

Ps. I do note the concerns of an amp meter off a dynamo. Will keep everyone updated as I proceed or fail.

Tony

[Tony]

John, Thank you for taking the time to check your volt meter. I have been looking at the Smith meter you recommend and I think is is a good as gets to going down volt meter route.

[Tommd]

I find it interesting that in replacing the 30 amp generator with a 60 amp dynator , there is a concern of upgrading the old amp meter with a 60 amp meter, but there is no concern about any of the other wires being upgraded. It seems to me I would either be concerned about both or neither.
Tom

[Tony]

!Hi Tom, You are right about upgrading the wiring, however the Dynamator is a 45amp rating not 60amp. By going for a 60 amp Guage as suggested by Stuart it is a belt and braces approach.
I am still looking at the options if to go amp or volt meter.

Tony

[johnetype]

Tom got the can of worms out so to speak, so it's time to pry open the lid

Moving from dynamos to alternators raised a set of issues that arose from having double or more power available and the opportunity for that to destroy batteries or cause fires.

The first was the need (and expense) for heavier duty wires between the alternator and the battery.

If you have a dashboard mounted ammeter those wires have longer runs and the ammeter has to handle greater currents. It also becomes an even less useful instrument because small current changes cause less movement so the ammeter isn't really telling you anything. You can't see any indicative small changes and if you do so it jerking around the 60 amp end stop it's time to get the fire extinguisher out.

The other challenge is voltage control. With more power available it became more important to keep the voltage across the battery in check so as not to boil it dry. Fortunately electronic regulators came in at the same time. Dynamos and their associated regulator are electromechanical devices, you can't have a working alternator without electronics. A long run of cable with its resistance and the added resistance of an ammeter makes voltage control more difficult. There are ways around it (remote voltage sensing etc.) but it's more complication and in those early days of electronics the whole system going into oscillation was a real risk.

The simple, surefire solution was the shortest length possible of heavy duty cable directly between the alternator and the battery.

With an alternator you were never going to run out of charging current so an ammeter was superfluous with the ignition warning light enough to tell you if you were charging the battery or not.

However, for Jaguar their particular warning light implementation in those early days of alternators was the least reliable part of the whole system when they moved to implementing alternators and they'd also got a hole in the dashboard they weren't about to redesign so enter the voltmeter to take it's place. Not particularly more expensive than an ammeter, saving on extra cable costs and wiring loom burnout costs and served the purpose of keeping the driver thinking he or she were engaged and usefully backing up the unreliability of the ignition warning light.

[Tony]

Well I have bitten the bullet with a positive Dynamator and gone down the Holden volt Guage route. Not sure I like the battery symbol or that I have to either spray the bezel black or see if my old one will swap out.
Just got to sort out the wiring in the least disruptive way keeping the old regulator as a junction box and maybe to hide the relay required. That’s a job for tomorrow

[caveman]

Hi Tony,
Did you consider Caerbont Automotive Gauges. There’s plenty of information on the forum and they are very helpful. Their website doesn’t show the Lucas Voltmeter, I contacted them separately and they are a perfect solution.

viewtopic.php?f=3&t=16418&p=153249&hilit=Gauge#p153249

https://www.smiths-instruments.co.uk/mo ... ar-e-type/

[Tony]

Yes, I messaged them but have not had a reply. There is a 4 week delay I believe which I could have got around by just doing without an amp/volt meter for the period.

Thanks for the advise and if the battery symbol annoys me I can always get a Caernont Guage.

Tony

[Tony]

Well, received my Holden ( Caurbont) volt Guage with brass bezel and battery symbol.

Managed to tee cut out the battery symbol and used my old series 1 bezel to match the other instruments.
As good as I can get it to match. It will have to do for now.

Tony

[Tony]

I have tried to post photo but the site throws me out and I have to keep logging back in again losing all my message. So now I copy my message , log in again, paste the message and send again. No idea what happens to the photo

Tony

[caveman]

I had the same problem Tony when I replied on Sunday. I ended up logging in twice and giving up on the photo I had lined up. Maybe there was maintenance going on as this forum is usually solid. Glad you got sorted, you must have the shiniest voltmeter in the UK

[Tony]

Hi Steve, it’s a bit of a pain not being able to post photos. However if things improve I will try and update the post. Just got to wire everything in now, so that will be interesting.

Tony