[Ross Nicol]

Woke up in a sweat this morning thinking, that info I gave on this thread was wrong and doesn't make sense,wish I could remove it.Anyway I hope I haven't put anybody out and I don't mind you thinking Ross is a nuff nuff.
Best to go back to basics-
A good test for a charging system (in a car with alternator) is to place a voltmeter across the battery and you should get -

12v or less (without the motor running) This is the Battery voltage only

14.4v or close (with the motor running) This is the Alternator output voltage applied to the battery.

Now with the alternator voltage held constant at 14.4v and this voltage being higher than the Battery voltage we get current flow from the alternator to the battery ( a charging current).
A flat battery has a low internal resistance so the alternator will supply quite a high initial current (amps) to the battery.
As the battery charges and it's internal resistance rises, less current will flow to the battery and it will eventually reach a fully charged state where it will only require maintanence current from the Alternator.This is why an ammeter gauge is good as it shows current drain when the alternator is not able to keep up. If the gauge reads in the green or to the right of centre with all electric circuits in the car switched on ( motor running),then you can say the alternator has the capacity to run the car and charge the battery too.Worst case is when the alternator does not have enough capacity left, after running the cars normal circuits to charge the Battery,result flat battery sooner than later.
Obviously the Battery voltage change can only be minimal (due to voltage drop when the charging current varies) and this is why a voltage test at the battery is a good indication of alternator operation.I'll find out more about the Battery sense wire on these new alternators and post what I find.Sorry again for the mis-information
Ross