[s-cars] Need Electrical Help

[Charlie Smith]

I've got a peculiar situation, that I think is caused by a high
resistance connection somewhere.  The question is WHERE?

The symptoms -

The engine cranks fast and starts fine.  On first starting, the S6 
voltmeter reads about 14 Volts, as I'd expect.  This tapers down to 
maybe 13 Volts after running a couple of minutes.

When I put a load on the electrical system, the voltmeter's reading
drops down a volt or two.  A load like turning on the headlights,
or when a relay related to the A/C clicks under the dash ... my guess
it's for the compressor clutch or the radiator fan.  Either is enough
to knock the bottom out of the voltmeter's reading ... sometimes below 
12 volts.

Any suggestions on where I should start looking?  I know, first put a 
voltmeter across the battery and see what it reads while the voltmeter 
in the dash is pulling it's stunts.  My bet is the battery voltage is 
stable, given how well the engine cranks while starting.

    - Charlie