Seasons Greetings, All!

My 1985 300D has a ghost in the charging system. My alternator is a new Bosch, new voltage regulator and the battery is new as well. I can drive around for days during the day with no symptoms. It would seem the battery maintains its charge just fine, and then the battery will suddenly turn up dead, usually at night. I'll run an errand, come out and the car won't start, after driving fine for a week or so, day and night.

I did tests on the system yesterday and everything looked fine. Results similar to this morning's tests below. I drove the car for three miles, checked voltage at the battery with the car running (idling, at 2000RPM, with headlights, without) and the highest reading I could get was 12.4 volts.

Could it be an intermittent short?

The battery light on the dash illuminates, and here are my multimeter tests:

Car Off cold: 12.12 volts
Cold Idle: 13.6 volts
1500 RPM cold: 14.25 volts
Warm Idle: 14.3 volts
1500 to 200 RPM warm: 14.4 volts
Idle w/ high beams: 14.04 volts
Idle w/ high beams + blower: 12.05 volts
2000 RPM w/ high beams + blower: 13.9 volts
Idle w. high beams + fog lights + blower: 12.03 volts
Car Off after 15 minutes of testing: 12.4 volts

Thanks for any input...

Chip