Well, let's add this strange symptom to the mix.  I was just driving
along and noticed my tach bounce around a few times.  I was under
load, at about 3800rpm, and it bounced down to 3500 a couple times
then back up to 3800, then down almost to 3000 and back up.  I tried
turning the cruise off and on and it had no effect.  I also felt no
hesitation when this happened.

I also looked at the audiovox instructions and wondered if I could
eliminate some factors by switching it to just use the tach signal
and not the speed sensor, or temporarily disabling the brake light
circuit.  I know the tach signal setup is not going to work very well
on an AT vehicle but might be worth a try?

Edward

>--- On Sun, 11/4/12, Edward Maglott <emaglott3@GMAIL.COM> wrote:
>
>From: Edward Maglott <emaglott3@GMAIL.COM>
>Subject: Re: troubleshooting Audiovox Cruise Control
>To: vanagon@GERRY.VANAGON.COM
>Date: Sunday, November 4, 2012, 8:41 AM
>
>Thanks everybody for the tips on troubleshooting.  I'm not sure of
>the of logic behind a low vacuum situation causing it to
>disengage.  My understanding is that it disengages for brake
>application, rapid rpm change, or the whole thing being turned
>off.  Also I assume it disengages when it gets weird signals from the
>speed sensor.
>
>More info:  The unit used to work very well.  It could not get the
>throttle way open, especially up hill, due to drop in vacuum I
>assumed.  But that was not a situation I wanted to use it
>anyway.  The onset of this problem was gradual.  There was a period
>where it got very erratic about when it would disengage.  During that
>time I tested all kinds of situations to see what was common and
>didn't come up with anything.  Hitting bumps in the road was not a
>factor.  Low Vacuum situations were not a factor.   On uphills, I
>could "help it" by putting my foot on the gas and when I got to the
>top of the hill it would take over and stay engaged.  I tried riding
>my foot lightly on the gas pedal to see if it was letting go of the
>throttle or pressing it hard right before it disengaged.  It wasn't.
>Sometimes it would not disengage for 30 minutes, other times a few
>seconds.  Very odd.  One time a few years ago during a trip with lots
>of interstate, it got to the point it was really not working much at
>all.   I stopped and went through all the audiovox checks of the
>wires.  They came out fine and put it all back together and then it
>worked better for a while.  Yesterday when I dug into this, there
>were times when the unit would not turn on at all, or at least it's
>little pilot light wouldn't illuminate.  I had never seen that
>symptom before.  Again, after doing the wire checks, it turned on and
>stayed on fine.
>
>Edward
>
>
>
>
>At 10:03 AM 11/4/2012, Richard Koerner wrote:
> >Ed, I've got the Audiovox CCS-100 on my 85 manual Vanagon.  I use an
> >accumulator purchased from Napa (just good practice to have an
> >abundant vacuum supply).  But sometimes the cruise control would
> >disengage--I noticed it would happen after going after some bump in
> >the road.  I think the root cause was that the bracket holding the
> >sensor would flex and oscillate, momentarily increasing the distance
> >between magnets and sensor, and the CC would lose itself.
> >
> >Simple solution:  STRONG magnets and a STRONG bracket.  I replaced
> >the wimpy magnets in the kit with some rare-earth  (neodymium)
> >magnets available at
> <http://www.gaussboys.com/>http://www.gaussboys.com/ or similar, google to
> >find a source maybe a hobby shop.  And a really stiff and strong
> >bracket of heavy gauge steel I had laying around (Home Depot or Ace
> >Hardware) to support the sensor in close proximity to the rotating magnets.
> >
> >Excellent results!!!  My cruise control NEVER drops out
> >anymore.  And I think having the vacuum accumulator makes for
> >INSTANT response when I push the button---very solid.  A real
> >pleasure to drive.  I'm really sold on that Audiovox unit.
> >
> >Rich
> >San Diego
> >
> >
> >
> >--- On Sat, 11/3/12, Edward Maglott <emaglott3@GMAIL.COM> wrote:
> >
> >From: Edward Maglott <emaglott3@GMAIL.COM>
> >Subject: troubleshooting Audiovox Cruise Control
> >To: vanagon@GERRY.VANAGON.COM
> >Date: Saturday, November 3, 2012, 7:33 PM
> >
> >hello, I have one of the usual aftermarket Audiovox cruise controls
> >on my 86 with AT.  I think it's model CCS-100?  I use the magnet
> >speed sensor kit on my drive shaft.  It's not working well.  It
> >engages briefly and then immediately disengages.  It will then
> >attempt to resume to that speed if I press that button, but
> >immediately disengage.  That makes me think that it is at least
> >remembering the speed I set it to.  I've gone through the
> >troubleshooting of all the wires as the instruction manual specifies,
> >and everything is good.  I'm wondering if I could devise some way to
> >monitor it from the driver's seat to figure out what is going
> >on.  Thanks for any advice.
> >
> >Edward