Lotus Elan

Adding Ammeter to Elan S4

PostPost by: jbeach » Mon Nov 11, 2019 5:09 pm

Dear Elan Community,

I have recently realized I yearn for the peace of mind an ammeter would give me during my ever-more-frequent drives through the countryside and in the somewhat-nearby North Carolina mountains. I am on the cusp of ordering a new dashboard (from Prestige) and, for obvious reasons, that purchase is driving this decision.

I have an electronic ignition system (Pertronix) and a modern Japanese alternator.

Please share your general thoughts on adding an ammeter to my electrical system. Will it be difficult to find one that matches my other standard Elan instruments? What are the sources and what particular model/style, etc. should I order? Can you please generally describe how an ammeter would be wired into my system? What are the challenges? What advice can you offer to make the job easier and more successful?

As always, many thanks!!

-John
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PostPost by: steve lyle » Mon Nov 11, 2019 5:39 pm

FWIW, I'd recommend a voltmeter instead.

To wire in an ammeter you need to feed the output of the alternator/generator to the meter in the dash, then back to the starter solenoid. It's a heavy wire, and a long, likely unfused, run.

There's a reason modern cars use voltmeters. Just wire it from the green circuit to ground, and you're good. If you see 14 volts or so, your alternator/generator is charging the battery.

Alternatively, there are voltmeters that plug into cigarette lighters, good for the occasional check.
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PostPost by: billwill » Mon Nov 11, 2019 5:41 pm

An ammeter is basically inserted into the wiring in the thick brown wire that goes from the starter solenoid to all the rest of the electrics.

i.e that wire is cut in two and the cut ends connect to the two terminals of the ammeter. The ammeter may also need a ground wire and a supply to its internal light bulb for night use. That will come by connecting into one of the wires supplying lights on the other instruments. You may need to swap over the wires on the ammeter terminals if it shows charge instead of discharge when you turn the headlights on (with engine stopped).

NB: The existing thick brown wire might not be long enough to split in this way so you might need to get some more thick brown wire and connectors etc to make this circuit.
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PostPost by: billwill » Mon Nov 11, 2019 5:46 pm

steve lyle wrote:FWIW, I'd recommend a voltmeter instead.

To wire in an ammeter you need to feed the output of the alternator/generator to the meter in the dash, then back to the starter solenoid. It's a heavy wire, and a long, likely unfused, run.

There's a reason modern cars use voltmeters. Just wire it from the green circuit to ground, and you're good. If you see 14 volts or so, your alternator/generator is charging the battery.

Alternatively, there are voltmeters that plug into cigarette lighters, good for the occasional check.



No that's not the best place to insert an ammeter that will only show the charging current not the discharging current from lights, ignition and radios etc.

The best place is (as I said above) the thick brown wire from the starter solenoid to the rest of the electrics. The alternator current passes down this en-route to the battery while charging.
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PostPost by: nmauduit » Mon Nov 11, 2019 5:53 pm

I would not alter the dash for adding an ammeter (and am not sure what level of peace of mind it may offer)...

actually my S4 had one added by a previous owner and I removed it (not liking the idea of the charging current going forth and back from the dash), then had a gaping hole ... which I eventally filled with an oil pressure warning light.
Smiths had ameters/vmeters of that era that would suit the design, possibly the plus2 version may have a similar font as the S4...

if you are set to have an instrument showing charging, I think you could to find a modern instrument (sensor + remote digital indicator?) that could be mounted semi hidden (ash tray, below dash etc) while you get more confident that your alternator is doing the job. I would think a modern alternator more reliable than most of the rest of the Lucas powered system ;) or battery...
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PostPost by: steve lyle » Mon Nov 11, 2019 6:24 pm

billwill wrote:
steve lyle wrote:FWIW, I'd recommend a voltmeter instead.

To wire in an ammeter you need to feed the output of the alternator/generator to the meter in the dash, then back to the starter solenoid. It's a heavy wire, and a long, likely unfused, run.

There's a reason modern cars use voltmeters. Just wire it from the green circuit to ground, and you're good. If you see 14 volts or so, your alternator/generator is charging the battery.

Alternatively, there are voltmeters that plug into cigarette lighters, good for the occasional check.



No that's not the best place to insert an ammeter that will only show the charging current not the discharging current from lights, ignition and radios etc.

The best place is (as I said above) the thick brown wire from the starter solenoid to the rest of the electrics. The alternator current passes down this en-route to the battery while charging.


If you want to know if the alternator is producing current, you'll put the ammeter where I suggested.

If you want to know the amps the car is using, you'll put the ammeter where you suggested.

I believe the OP wanted to know if his alternator was healthy, hence my suggestion.

If he puts it where you're suggesting, he won't know that his alternator isn't producing any output until his car battery dies and the car stops - or he notices that the ignition light is on (which, of course, is an alternator health indicator he already has).

BTW, the charging current does not pass through "the thick brown wire from the starter solenoid to the rest of the electrics" - from the starter solenoid it goes directly to the battery through the heavy cable that runs from the battery + terminal to the solenoid.
Last edited by steve lyle on Mon Nov 11, 2019 7:29 pm, edited 1 time in total.
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PostPost by: englishmaninwales » Mon Nov 11, 2019 7:10 pm

“BTW, the charging current does not pass through "the thick brown wire from the starter solenoid to the rest of the electrics" - from the starter solenoid it goes directly to the battery through the heavy cable that runs from the battery + terminal to the solenoid.“

+1
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PostPost by: billwill » Tue Nov 12, 2019 1:04 am

englishmaninwales wrote:“BTW, the charging current does not pass through "the thick brown wire from the starter solenoid to the rest of the electrics" - from the starter solenoid it goes directly to the battery through the heavy cable that runs from the battery + terminal to the solenoid.“

+1
Malcolm



It does on mine and on all the circuits that I have seen for changing a dynamo to an alternator.
(the alternator wire output goes to the place in the old dynamo circuit where the controller was {even if it is retained it is a dummy not in the active circuit})

And on all modern wiring diagrams for cars. It needs to be done this way to show both charge & discharge on an ammeter. The ammeter being a centre zero one of course.

It seems you two have a non-standard Alternator arrangement.

See: viewtopic.php?f=38&t=36823&start=
and RDENT's wiring instructions:
download/file.php?id=42824
or:
viewtopic.php?f=38&t=38963&start=15


........

ah, I see you probably followed the guide here:
http://www.lotuselan.net/wiki/Elan_Alte ... Conversion
or this:
viewtopic.php?f=38&t=28679&start=
Not a good idea in my opinion.

Take your pick of topics on this forum covering Alternator installation:
https://www.google.com/search?q=how+to+ ... uselan.net


Hey ho, do whatever the mood takes you.
https://www.google.com/search?q=alterna ... IQ_AUIESgB
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PostPost by: m750rider » Wed Nov 13, 2019 5:42 pm

John

Nisonger Instruments sells Smiths gauges. Their ammeter is the same size as the fuel, oil/water gauges.

That's is what I have on my car - been there since I bought it in 1973, on the right side of the radio.

And yes, it's nice to have in addition to the red light on the tach.

Good luck, Randy makes great dashboards, have putting it in.

Bob

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PostPost by: stugilmour » Wed Nov 13, 2019 9:12 pm

John, I would also recommend using a voltmeter.

The Plus 2 WSM recommended changing out the dash-mounted ammeter (stock in earlier cars) to a Smiths voltmeter (or “Battery Condition Gauge” as it was actually known) if the owner/dealer upgraded from a generator to an alternator. I have attached a picture of a typical gauge; note the small curved cover over the needle movement is a different shape than the other Smiths gauges.

On occasion I saw Smiths voltmeters for sale with the matching look, but was unable to get one when I changed mine. I dismantled the voltmeter I purchased and swapped in the cover from my stock ammeter so everything matches better. The used voltmeter I purchased is pretty slow acting and approximate, needs a few taps to get going sometimes on cold mornings, and fills the Randy Keller sourced Plus 2 dash out great, which was the most important thing for me.

I also have a small digital voltmeter I can plug into the cigarette lighter. This works well enough, as long as you accept it as ‘accurate but not precise’. By that I mean it tends to read a bit low, presumably due to losses in the fuses and other wiring & connections to the lighter socket. However, it would be sufficient to let you know if the voltage was less than ‘normal’, and normal will be apparent after a bit of use.

So, as usual, your car, your choice. My recommendation would be to try out a cheap lighter voltmeter first and see how you get on with it. I would not want to add a non-stock hole to the dash, but rather add a small digital voltmeter in some Inconspicuous spot under the dash if I wanted a purposefully wired voltmeter. Really if the wiring and charging system are sorted and in good nick the voltage readings are pretty much stable anyway.

Plus one on the ease of wiring a voltmeter rather than an ammeter. Giant unfused brown wire next to dash kindling in a plastic car, not so great. I wired my dash voltmeter to White - Hot in run & start, unfused rather than Green - Hot in run & start, fused to prevent a bunch of losses, but either scheme will work.

HTH

Stu

PS Randy Keller makes a great dash.
Attachments
dafe0bd5-7636-41b0-a197-2eee2f6304d6.jpeg
This is a Smiths ammeter that looks more like the one in my Plus 2. I cannot recall if it was only a 30 amp range? Note the movement direction is backwards to what I would expect; my thinking being reading ‘high to the right’ is usually a good thing. This actually caught me out when I first got my car. I thought I was well in the charging zone until I sputtered to a stop! We were actually discharging the battery for about an hour of shakedown running as we missed the + and - signs.
dafe0bd5-7636-41b0-a197-2eee2f6304d6.jpeg (39.33 KiB) Viewed 958 times
252d62d0-fbe4-4792-b870-f85733eada81.jpeg
And to be complete, here is a typical Smiths ammeter I found online. Note this one is not quite right for a Plus 2, as the gauge moves in reverse to the kne that was in my car originally. If you do install an ammeter, this is the baby I would try for with 60 amp range and ‘reversed’ movement.
252d62d0-fbe4-4792-b870-f85733eada81.jpeg (46.97 KiB) Viewed 959 times
0930c34f-b576-4911-991a-6562deace155.png and
This is a picture of a Smiths Battery Condition Gauge that would match your fuel gauge better. Note the squared off movement cover. When I was looking I couldn’t find one for sale. Also note that the used gauges on eBay have various types of chrome or black bezels, so watch for that.
999328f4-6479-4c61-a4f8-10544c2721c5.jpeg
Picture of a typical Smiths Battery Condition Gauge or voltmeter. Note the rounded shape to the cover over the top of the needle movement. Note this is similar to the drawing in the Plus 2 WSM section on upgrading from the ammeter when installing an alternator, even though it would not match the other gauges very well.
999328f4-6479-4c61-a4f8-10544c2721c5.jpeg (28.66 KiB) Viewed 962 times
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PostPost by: MarkDa » Thu Nov 14, 2019 9:53 am

Like others I'd suggest a voltmeter.
Dynamo outputs were generally quite low especially at low rpm so it was quite possible that they wouldn't "keep up' when lights and heater fan on.
So it was useful to be able to see net current status - although of course some indication would be available from brightness of lights :D .
As others have said the charge light does this and we will all have experienced low indicator flashing frequency at tickover.
In general terms alternators produce much more current than a dynamo and a far better indicator of charge circuit health is a voltmeter.
Last edited by MarkDa on Sat Nov 16, 2019 7:12 am, edited 1 time in total.
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PostPost by: jbeach » Sat Nov 16, 2019 5:02 am

Well. Thank you.

This is an amazingly informative outpouring of information. I clearly do not understand how an ammeter functions! I always just figured if the needle was on the positive side, you were reading the net surplus of electricity being generated vs used; if on the negative, the net deficit; if in the positive, your battery was charging (good) but, if in the negative, your battery was discharging (bad, and ultimately unsustainable).

Based on this understanding, I also always felt that an ammeter was more useful than a voltmeter, because if you’re producing 12 volts, your voltmeter looks pretty good, but if you’re using 13, you’re headed for a dead battery and a voltmeter wouldn’t necessarily tell you that.

But I’ll have to admit, I’ve never really given it much thought and I’m clearly not an electrical engineer.

BUT, I don’t like the idea of routing another heavy wire from the engine compartment to behind my dash, which it appears I must do in order to install an ammeter.

Decisions, decisions!

-John
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PostPost by: StressCraxx » Sat Nov 16, 2019 5:46 am

I would agree a voltmeter is a good choice, but the "charge light" is pretty useful if you learn to understand it.

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PostPost by: steve lyle » Sat Nov 16, 2019 6:50 am

John,

One thing to consider - it's not uncommon to hear of fires started by failed ammeter installations. Lots of threads out there on other boards if you search. But I've never heard of a catastrophe related to a voltmeter.

A clarification of your post. You dont "use" volts, like you do amps. Using the hydraulic analogy, amps are gallons, volts are pressure. So a battery is a source of gallons at a particular pressure, until the alternator or generator kicks in and replaces it. A battery will max out at 12.5 volts or so. An alternator is going to be regulated to produce 13-14v, so it can charge (i.e., flow current to) the battery. If you're using a voltmeter, engine off, you'll see the base battery voltage. If you then start the car and don't see something significantly higher than that, you've got a problem (assuming you've got an alternator, which produces voltage at relatively low engine speeds.

The ignition light is sort of a simple analog voltmeter. The ignition light has one contact at battery +, and one at the alternator output. With the key on and the engine off, the ignition light is on because the battery voltage is 12.5 or so and the alternator output is at ground, so current flows and the bulb lights. With the engine started, the light goes out because the battery voltage is essentially matched by the alternator voltage - there isn't enough voltage difference to flow enough current to light the bulb. Should the alternator fail, and the voltage produced by the alternator starts to drop significantly below the battery, the light will start to glow - the brighter it glows, the poorer the alternator is performing, because the larger the voltage difference the greater the current flow and the brighter the light.

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PostPost by: billwill » Sun Nov 17, 2019 2:56 am

jbeach wrote:Well. Thank you.

This is an amazingly informative outpouring of information. I clearly do not understand how an ammeter functions! I always just figured if the needle was on the positive side, you were reading the net surplus of electricity being generated vs used; if on the negative, the net deficit; if in the positive, your battery was charging (good) but, if in the negative, your battery was discharging (bad, and ultimately unsustainable).


That's correct

jbeach wrote:Based on this understanding, I also always felt that an ammeter was more useful than a voltmeter, because if you’re producing 12 volts, your voltmeter looks pretty good, but if you’re using 13, you’re headed for a dead battery and a voltmeter wouldn’t necessarily tell you that.


Volts don't work like that , but in my opinion an ammeter is much more useful than a voltmeter as a diagnostic fitting on a vehicle.

jbeach wrote:But I’ll have to admit, I’ve never really given it much thought and I’m clearly not an electrical engineer.

BUT, I don’t like the idea of routing another heavy wire from the engine compartment to behind my dash, which it appears I must do in order to install an ammeter.

Decisions, decisions!

-John


No you wire the the main alternator output to the point on the fuse box where the thick brown wire comes from the solenoid, (this causes both the charging & discharging current to flow {in opposite directions} in the thick brown wire. Then you use Famous Frank's easy way to add a single extra wire from the vicinity of the solenoid to the ammeter & back. The link is above. When I say thick here it is nowhere near as thick as the big fat black wire from battery to solenoid that carries the hundreds of amps for the starter motor.

~~~~~

An ammeter in just the alternator wire will only tell you one thing, i.e whether the alternator is supplying current or not, you won't know if any of that is going into the battery or is all being used up by the ignition and lights etc. An ammeter wired to show both charge and discharge currents will also reveal problems with headlights, sidelights, signal lights, radio etc etc. It won't actually show whether a battery is fully charged, that's what a voltmeter would do (but practically ALL that a voltmeter can do).

With a properly wired ammeter, on starting the engine, you will see it charge for a short while as it restores the charge in the battery that has been used to start the car, then as described by yourself above, it will show zero charge/discharge indicating that the alternator/dynamo is generating exactly the right amount of electricity to supply your ignition and accessories.

If it shows a continuous discharge your battery is running down, if it shows a continuous charge, there is either an electric leak somewhere near the battery or the alternator/dynamo controller is not working properly and will eventually ruin your battery (it is electrolyzing the liquid into hydrogen & whatever and will dry out or explode).


PS: I am an electrical engineer. :D
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