Does the Rev-Counter work properly? does it do strange things like flick to the red-line for no apparent reason? (Especially when you try cranking the engine) Does it just 'trip out' or stop working whilst driving?
The Rev-counter takes its signal from the alternator frequency. If the regulator 'goes' then the tacho will often just stop working.
If it does strange things, like flicking to the red line, or wobbling about at steady speed, or dropping out then coming back, it can be pointing to the windings breaking down.
It's NOT a sure fire test, but if you are having intermittent electrical problems, then the rev-counter can be a good director to the alternator, as it is showing up stuff thats going on while you drive, and as the windings get hot etc, that wont always show up when you test the thing cold, on the drive, and not under the same load or temps as when driven.
Useful little widget you can get from Halfords is an alternator tester, just clips to the battery, and is essentially a 0-20v volt-meter.
Using the Multi-meter on 0-20 (or higher) range DC, you CAN test in teh 'dynamic' state, (ie driving!) by extending the test leads through door seal and bonnet gap, and having the meter on the passenger seat.
