[Vwdiesel] Diagnosing a failed alternator, or?

[Val Christian]

Has an ALT light on a 02 TDI Jetta, and presumed I had a failed overrunning
clutch, or possibly brushes.

On test run, (saving lots of details) it was found that the instrument panel
would go dead, but the ALT light would come on.  No voltmeter in hand, but 
looking at the interior lamp temperature, and adding load, and shedding load,
it appears that the ALT may be working OK.

I found the car with lots of frost on the interior.  The normal driver only 
uses defrost heat, and then minimal, and relies on heated seats for warmth.
The car is idling (temp is up to 12F) and I have lots of load on, and the
blower on low and the temp setting on high, in an attempt to dry the car out.

Has anyone had a similar problem?

Thanks.