David Beierl wrote:

> But surely you have a scope?

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.

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.

I'm going to plug the van into the household Mains and let my onboard
battery charger take the deep cycle to 100% and see if the surging
occurs with a full house battery.

--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
Bend, OR
KG6RCR