Years ago I fitted an alternator and an ammeter (along with other gauges) in Mog. I find the ammeter absolutely indispensable, because it instantly shows if a circuit is functioning or not - e.g., when the pressure-actuated brake light switches packed up, I knew immediately. However, the ammeter has never displayed a charge! It shows discharges just fine, in proportion with what I expect for a given circuit's amperage demand. The alternator gives out plenty of juice and I never have an ignition warning light (except when the engine's not running, of course).
If the ammeter connections were simply reversed, I'd expect discharges to not add up evenly - that is, as the system gained charge the needle would move toward discharge, and as more circuits were activated it'd move toward charge. But the needle only twitches when circuits are activated, and only toward the discharge side.
I imagine I've wired something incorrectly (though the system charges and discharges just fine). What do you suppose I've done?
The way to a man's heart may be making food, but the way to my heart is buying me car parts!
Come read about my Minor at An American Moggie.
I have the same query myself with 2 different cars which I inherited with purchases. One is a Smiths the other a Tim.
I just thought that they were both U/S? Both show discharge, but only a tiny flicker into the charge section at start up.
Simply that the alternator wad connected directly to the battery, not through the ammeter? Seems to be the obvious and simplest explanation. Have a look!
Possibly correct, but as I said I inherited them already fitted, but will obviously check. Thought that it was too much of a coincidence with 2 with the same system used..ie both had alternator retrofitted.
If the battery is well-charged and holding a good voltage, perhaps the alternator is only giving it a trickle charge, and not enough to be visible on the needle?
Brian
"Jodie". '67 Traveller, 1275, discs, suspension mods etc.
Wiring checked--all good. Read some other forums on this subject, and it seems that it is how others have found them, and that it is better to fit a battery meter when connected to alternator.
I've never had much luck using an ammeter with an alternator. My old Hillman Hunter (factory fitted alternator and factory fitted ammeter) always read '0' except when cranking on the starter ('-30') or when parked with the hazard lights flashing (an annoyingly regular occurence) which gave '0' to '-15' in conjunction with the on/off flashing of the lights.
I fitted a volt meter to a Marina which luckily gave me warning when the alternator started slowly cooking the battery.
Just a thought, but where exactly is the ammeter in the circuit?
If you're using the old voltage regulator as a junction box, there's a possibility that there's an undesirable link causing false readings, or even not charging as it should.
Here's the wiring diagram from my MG TD which had a factory fitted ammeter and dynamo. The voltage regulator is the same as the Moggy. Although the dynamo can produce 22 amps the ammeter just barely goes into the positive range when the revs are above 1200rpm.
Here's a useful article. http://www.mossmotoring.com/pint-size-p ... regulator/
It shows the connection of the ammeter.
Regards
Declan
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if he use Lucas Regulator (Control box) with Dynamo I can help him. Red light "ON'' mean , No power (Voltage ) Connection . (Power not come inside to the control box) . Ask any questions from me, if you have Dynamo and Control box.
I've only ever changed from dynamo to alternator on six engines, I think. Cortina, Anglia, Cortina, Cletrac HG a Mini and now the MM.. Probably helped others fit another dozen over the years.
On every one of those, I have connected the alternator output directly (or indirectly via the starter solenoid terminal) to the live terminal on the battery. No exceptions - not one through the ammeter. Even if an ammeter were fitted originally, some of the alternators I have fitted may well have more than 'pegged' the ammeter at full charge. The dynamo wiring is likely of insufficient guage for the extra current load, particularly if going through the loom.
As stated earlier, if the alternator output goes directly to the battery, there will be no charge indication on the ammeter.
I've noticed that a lot of the American restorations and hot rods these days which have a 'full set' of dials tend to go for a voltmeter rather than an ammeter.
Brian
"Jodie". '67 Traveller, 1275, discs, suspension mods etc.
A volt meter is far better than an ammeter. You can wire it in anywhere convenient and only use small gauge wire. If the alternator/ dynamo is charging the meter will show a reading above 12.4 volts. It will also show if the charging circuit is over charging as well and if you read it right will show if your battery is due for renewing. It's a far better means of keeping an eye on the electrical system.
The change, over the years, from ammeter to voltmeter is simple - the fitment of alternators.
In the days of the dynamo, the charge rate was dependent on speed of the engine as well as the state of charge of the battery. One could easily run with a discharge situation if loads were high. Because the alternator should produce high power output at anything but very low speed (engine idle speed, effectively) the generation rate, after initial replenishment of starting power, will normally be controlled at the load value after very little running time. Batteries of the ‘dynamo’ era would withstand being discharged much deeper than modern items (and also overcharging, as the vehicle owner regularly checked and added distilled water as the electrolyte level dropped.
I have an annoying Saxo, which is fitted with pulley sizes such that net charging ceases at engine idle. Headlights go dim at every time one brakes to a standstill in traffic. An extra 1-200rpm engine speed provides good generation. Citroen only needed to fit a slightly larger crank pulley or slightly smaller alternator pulley, to avoid this annoying trait.
Thanks all for the obvious identification! I didn't feel like going out and looking at my wiring in this zero degF weather.
On the subject of voltmeters: a voltmeter is deficient, compared to an ammeter, in one crucial area: shorts! If you have an electrical short, you know instantly on an ammeter. With a voltmeter you only know when smoke appears in the cabin. I may add a voltmeter one day, but I will never be without an ammeter on my Minor. As I indicated in my first post, I also find the ammeter's display of power consumption on individual circuits really useful, as I can tell immediately if I have a burnt-out bulb, nonfunctional switch, etc.
A voltmeter tells you about the state of charge of the battery, but says nothing about the other circuits of the car, as far as I understand. If Mog's battery is undercharging, I'll know from the IGN warning light (or from sluggish starting...).
The way to a man's heart may be making food, but the way to my heart is buying me car parts!
Come read about my Minor at An American Moggie.
We have had an ammeter in the Minor for the last 40+ years, and would not be without it. But the there is a 'BUT'. If you want to see the full story of what is flowing into and out of the battery and the rest of the circuits, the main output wiring from the alternator has to be connected to the ammeter first, and then on to the battery. Also the connections to the rest of the car have to be connected directly to the ammeter. This means that there have to be some heavy cables passing through the bulkhead twice for the ammeter to work 'fully'.
Connecting the alternator directly to the battery avoids much of this, but does mean that the ammeter will only show 'discharge', and no 'charge'. I think this may be why ammeters are sometimes fitted this way, to avoid the really heavy cables passing through the bulkhead.
When the last production of the Minor was fitted with an alternator and ammeter, it showed any net 'charge' into the battery, but only the 'discharge' for the ignition controlled circuits - the 'always on' circuits bypassed the ammeter completely!
Fitting a voltmeter avoids any need for heavy cables, is a very much simpler fit and significantly reduces the fire/danger risk from unfused heavy cables shorting out. Also the output from alternators today is 3 and 4 times the level for early ones - the Lucas ACR15 was all of 28A output, whereas a 'modern' car will have anything from 70A to 100A+. Even the recent replacement ACR for the Minor has a 75A output. The ammeter is a 60-0-60 amp one, but has never shown more than about 40/50A charge for a few seconds after a cold start, but with everything on, on a cold winter's night (including a heated front screen), the alternator will be properly earning its living!
A short while after a start the battery is back to fully charged, and the ammeter will show only a very small charge of 1-2A. Even that goes down to 0A after a series of long runs on a few days' holiday. Turning on any accessory produces a very quick 'flick' before the regulator adjusts the alternator output to match the new load. Idling with headlights, wipers etc. on can create a small discharge with a heavy load, but once going very quickly goes back to near or actual zero. If it doesn't, and assuming that the regulator is working correctly, is an early sign that the battery is not in perfect health.
Properly fitted, with correctly sized cables, good terminations, bulkhead grommets and insulation where required, an ammeter is a very useful instrument to have, but anything else could be an incident waiting to happen, is which case a voltmeter is a simpler and safer bet.
