Date:         Sun, 8 Jun 2003 22:09:54 -0500
Reply-To:     boroko <marokus@VOYAGER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         boroko <marokus@VOYAGER.NET>
Subject:      Cruise Control troubleshooting: continued
Content-Type: text/plain; charset="iso-8859-1"

This is a response that I sent to Zoran.  Since it is long, I thought I'd offer it up for comment:
Mark




It's been a few years since I installed mine, but I'll try from memory.

The speed sensor is likely a coil of wire with a pole piece in the middle.
When a magnet passes this pole (internal to the Speedo) it should generate a
positive spike and then a negative spike.  They are going to be small, so
unless you have equipment to see it, you won't see much. You'll likely see a
slight bump on a meter needle if it's analog, or an erratic reading if it's
a digital meter.  Since it's only a coil, the failure seems unlikely.  One
thing that effects a sensor like this is it's distance from the magnet.  I
don't suggest a major troubleshooting, but if the screw has come loose, a
few tenths of an inch would cause it to not give a signal.

The things that are more likely to give you problems are the vacuum valves
at the pedals, as they are simply made, and the vacuum lines as they cover a
long distance from the front to the back of the van.  There are a number of
rubber interconnects that couple the plastic tubing and any one of them
leaking would stop the system from working.  A Mity-Vac (hand held vac pump)
would be helpful here.  You would have to pull from the engine compartment,
probably where the lines hook up to the pump, to see if the front is
holding. It should hold vac unless you have a leak.  Another vac test would
be to compress the diaphragm manually and hold your finger over the port.
If it stays collapsed, then it is holding and not the problem.

The system works by pumping a vacuum in the lines that are connected to the
diaphragm.  The control function is in the pump and controls a internal
valve that vents the vacuum, I believe, even with the pump running.  The one
that I got had a broken housing, so I had it open to repair it, otherwise,
you would have no clue that it is in there.  Any break in the vacuum
releases the diaphragm and stops the cruise.  The connections to the
hydraulic brake light switches probably works as a backup to the control
box.

When I got started in fixing things, an old mentor drilled into me to look
for the simplest things first.  Electronics go bad a lot less frequently
than one would think.  It is usually mechanical.  Leaks, broken wires at
places that they flex or rub, and connectors that wiggle lose or corrode.

If I can be of any more help, feel free.
Mark
----- Original Message -----
From: "Zoran Mladen" <zmaninco@yahoo.com>
To: "boroko" <marokus@voyager.net>
Sent: Sunday, June 08, 2003 8:15 PM
Subject: Re: Troubleshooting cruise control


> Wow, so I guess you understand the cruise control
> systems, eh???
>
> Is it possible to test the speed sensor?  Perhaps with
> a volt meter and running a drill in reverse?  Seems
> like something (resistance) should change as the speed
> changes.
>
> Thanx immensely for your help.
>
> Z
>
>
> --- boroko <marokus@voyager.net> wrote:
> > OK,
> >
> > The stock Cruise control takes it's speed reading
> > from the back of the
> > Speedometer.  A reluctance pick-up is screwed into
> > the back of the speedo
> > and can be seen with a small plug that has two wires
> > on it. It is removable
> > with a small screw or two.
> >
> > The pickup "reads" a small magnet or steel slug that
> > is already part of the
> > speedo whether it came with CC or not.  I installed
> > a stock CC system on one
> > of my '87's that came from a junker and along with
> > the rest of the system, I
> > had to add the sensor to the speedo.  I think I
> > found a sensor from a Jetta
> > or something of a similar year.
> >
> > The system basically consists of:
> >     The controls on the turn signal stalk,
> >     a control module behind the glove box,
> >     Vacuum switches on the pedals,
> >     the speed sensor in the speedo,
> >     a wiring pigtail that hooks into the brake light
> > switches on the master
> > cylinder,
> >     a pump in the rear valence on the right,
> >     A vacuum diaphragm and brackets that hook to the
> > throttle arm,
> >     and, two plastic vacuum hoses that feed vac to
> > the pedal switches and
> > (if they are held closed by the pedals) communicates
> > that vacuum back to the
> > pump in the back and the diaphragm.
> >
> > The chassis wiring was already present in mine from
> > the fuse box area to the
> > pump.  All I had to do was add the harness for the
> > control box, brake
> > switches, and the control box. Mount the pump and
> > diaphragm, pedal vac
> > switches, and the control box,  and plumb the vacuum
> > lines.
> >
> > The confusion may come in from Cruise Controls that
> > were not stock.  Since
> > they could not depend on a standard for speed sense
> > on different vehicles,
> > they usually mount magnets on a drive shaft and get
> > their speed signal from
> > there.
> > There may be other configurations that I'm not aware
> > of, but that's my
> > input.
> >
> > Mark Rokus
> >
> >
> > ----- Original Message -----
> > From: "Zoran Mladen" <zmaninco@yahoo.com>
> > To: "boroko" <marokus@VOYAGER.NET>
> > Sent: Sunday, June 08, 2003 4:06 PM
> > Subject: Re: Troubleshooting cruise control
> >
> >
> > > Hey there,
> > >
> > > Ok, tell me about these magnets.  I have another
> > guy
> > > telling me I need the magnets (which are not
> > there,
> > > nor is the mechanism to register them).
> > >
> > > Help!
> > >
> > > Thanx!
> > >
> > > Z
> > >
> > > --- boroko <marokus@VOYAGER.NET> wrote:
> > > > Hi Z,
> > > > The most common trouble that I have had with the
> > > > cruise is the vacuum
> > > > switches that contact the pedals not being held
> > > > closed enough.   On mine,
> > > > there was enough freeplay in the clutch pedal
> > that
> > > > if you let go of the
> > > > pedal hard enough (let it rebound without your
> > foot
> > > > on it) it would move the
> > > > switch in it's holder enough to not hold the
> > plunger
> > > > tight.  I reach down
> > > > and re-adjust the switch and the cruise works
> > again.
> > > >  I should re-bush the
> > > > pedal pivots and get rid of the problem, but
> > like
> > > > most problems, now that I
> > > > know what is causing it, I'm not as worried
> > about it
> > > > and I can get to work
> > > > for trips until I get to it.
> > > >
> > > > BTW, the speed pickup for a stock cruise is in
> > the
> > > > back of the speedometer
> > > > and does not require external magnets.
> > > >
> > > > Mark Rokus
> > > >
> > > > ----- Original Message -----
> > > > From: "Zoran Mladen" <zmaninco@YAHOO.COM>
> > > > To: <vanagon@GERRY.VANAGON.COM>
> > > > Sent: Sunday, June 08, 2003 1:43 AM
> > > > Subject: Troubleshooting cruise control
> > > >
> > > >
> > > > > What do folks recommend?
> > > > >
> > > > > I verified that the column switch is working
> > > > properly.
> > > > >  As well, I checked the wiring at the control
> > > > unit,
> > > > > and the proper hot wires and grounds are
> > there.
> > > > >
> > > > > How should I go about troubleshooting the
> > system?
> > > > >
> > > > > Z
> > > > >
> > > > > __________________________________
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