To get a true sense of what the alternator is putting out you have to
measure the voltage right at the alternator. There could be and often is
a large drop in the voltage seen at the battery but this is usually the
fault of the wiring. The way to tell is to measure at the alternator and
at the battery, compare them. Then turn on the headlights and heater fan
speed 2 and check the voltages at both again.

The Bosch alternators used in our VWs don't generally produce a higher
voltage at higher rpms than at idle so don't expect them to. If one
does, it is more than likely an indication of a problem.

Mark

Don Hanson wrote:
>    My bosch alternator,  a rebuild  just a few years old, is giving me 13.10
> +/- volts at the passenger side (starter) battery terminals.   I am thinking
> "new Voltage regulator"...right?  When I add rpms or load (turn on
> headlights)  nothing much changes with the voltage.  anyone care to comment
> or confirm that another regulator is the 'right stuff?"
>
>    Don Hanson
>