At 08:36 AM 5/21/2010, Mike \"Rocket J Squirrel\" wrote:
>... I noticed that the dash and headlights were brightening and
>dimming, just perceptively, and very regularly, with a period of
>slightly over a second
>
>... can anyone tell me if this sounds like an alternator voltage
>regulator thing? It does not vary with engine rpm.

I'm curious, too, because I've got some noise in the audio system
that cycles at roughly that rate.  I don't yet know what it is.  I
haven't tested whether it varies with engine RPM.

When I connect my Droid to the aftermarket stereo in my '84 Westy,
the audio sounds great.  Until I plug in the charger cable to the
Droid.  The charger cable is powered by a little Griffin USB car
charger, which I love, by the way:

http://www.amazon.com/exec/obidos/ASIN/B001Q2FM5E/sbw/

When I plug in the charger cable, I can hear a hissing, buzzing noise
in the speakers, constant but pulsing in volume once per second or
so.  It's inaudible except at high volume settings (on the stereo)
during silence from the Droid.

A classic ground loop, right?  The cigarette lighter plug isn't
grounded in the same place as the stereo, so weirdness ensues when I
run that potential through the Droid's power jack to the Droid's
audio jack and back to the stereo.  No surprise there.

But why does the noise cycle like that?  I thought maybe the ECU has
a sampling rate in its circuitry, or something.