At 06:33 PM 5/21/2010, Mike \"Rocket J Squirrel\" wrote:
>Mister Oscilloscope shows that the voltage surge is about 300mv in
>amplitude, occurs every 1.04 seconds, and is about 100ms in
>duration. None of these features change with additional circuit
>loading (e.g., turning on the headlights), nor with engine rpm.
>
>This doesn't sound to me like a voltage regulator problem.

Nope, me either.  Gotta be a load, and I think you've nailed it
below.  Though I'm curious that it's an increase and not a decrease.

>I wonder if I've got an active load of some sort pulling on the
>electrical generation system, such as my DC > DC battery charger
>which can haul up to 15A out of the system for charging the deep
>cycle house battery.

Lots of modern battery chargers will pulse-charge at more-or-less
full output once the battery leaves the deep-drained condition.

d