I think I know the answer. Even in generator cars it’s rarely seen as a helpful gauge. With headlights on it might barely dip to the negative, but what are you going to do?
On alternator cars it’s really just to fill up the hole, right?
Hadn’t the advent of better batteries taken care of most charging system concerns even before alternators?
Mine does tell me when I need to put the charger on the battery. That can happen during the summer because I wired the Coolcat fan to run on after shutdown. If the ammeter needle is deep into the charge side it means the battery has been run down. When the battery is fully charged then at speed the needle is only slightly into the charge side at speed.
I replaced mine with a voltmeter because I have a high amp alternator and the wires behind the ammeter were starting to cook. I ran the alternator wire direct to battery and then ran another power wire to run the voltmeter.
What I did with Tweety, too.
I believe it is of value to have some type of charge indicator on both generator or alternator systems. I would rate a voltmeter as providing the most information, ammeter as next, and charge indicator as least informative. But you should have some indication.
Tom
My understanding is an ammeter is not the apropriate instrument for an alternator
Why it was used by Jaguar engineers is not known to me
All that current going thru the cabin wiring is just a flat out bad idea
I know it would make the purist ill, but a cheap-ass digital voltmeter gauge is very useful, as it will indicate directly whether your battery is failing, nothing else will do this
I still like ammeters, preferably in addition to, not in lieu of, voltmeters. Ammeters tell you when the battery is being charged and when it’s being discharged. It’s particularly satisfying to me when I observe, after starting, a brief period of charge followed by a return to barely above zero–indicating a fully charged battery and working alternator and regulator.
IMO ammeters were replaced with voltmeters in cars precisely because of having to use thick, expensive wire, and to route it into the cabin. This was at the time when most instruments were being eliminated.
But the ideal solution, then and now, would be to use remote-sensing ammeters as is done in industry. Basically, a relatively sensitive ammeter (say, +/- 1 A) is in the cabin, wired with light gauge wire similar to what would be used for a voltmeter. Then, in the engine compartment, an ammeter shunt is installed in series with the cable into the battery terminal (except the starter). For a reading of +/- 100 Amperes, the shunt’s resistance would be 1/100 of the ammeter’s resistance. A length of battery cable itself could serve as the shunt. The ammeter is calibrated +/- 100 A but only 1% of that current actually enters the cabin.
One option is to bridge the two wires and safely insulate them then replace the ammeter with a later Smiths voltmeter. Wire one side to any green wire and the other to earth.
In my Series 2, I still use the original battery condition unit as supplied by Jaguar. In days of yore when I still ran with my (thrice rebuilt) Lucas alternator, it was very helpful.
It gave me a heads up when failure was imminent (often) and to find a safe place to pull off the highway. The comatose needle sliding into the discharge side coupled with the fading dash lights was a dead give away as to Mr. Lucas’ intentions.
Now, with a 65 amp Hitachi one-wire, it still gives yeoman service as the needle swings up smartly to the right and stays there. It also is a good fit with the other gauges, retaining the original factory dash lineup.
