To provide an (almost certain) explanation to the reason why your voltage
light stays on until you rev the engine...

The stationary, permanent magnets in alternators are very weak and 
you really have to get the rotor spinning before you can get 12V out
of your alternator, once you do, however, then the stator windings are
creating strong flux lines and the alternator has no trouble making 14V
at a low idle speed.

Cheers,

SStones,  Toronto Ont. (EL/('85GL))
<sstones@io.org>