[s-cars] Cruise control debugging

Sat May 28 10:36:27 EDT 2005

Brent,

The easiest way to get to it is to take out the glovebox and the kick panel.
There are a couple of options on how to get the glovebox out, one deals with
Torx bits in hard to get at places and one deals with prying off clips from
a piece of plastic.  I think I wound up doing a combination.  The plastic
and clips thing always bothers me on 13 year old plastic.

Once those two items are out it is a snap.

I have soldered test leads onto the circuit card after I took it out of the
box and all the signals are getting there fine even when it doesn't
set...hence my frustration.  My only possibility now is that the speedometer
signal isn't quite the right amplitude.  It only goes down to 0.8ish volts
or so rather than 0 and if it interfaced to a TTL logic gate then that might
not be low enough.  It may be that that the speedo connection that goes to
the CC unit from the dash isn't making good contact.  That's probably my
next place to go.

--Calvin

-----Original Message-----
From: Brent Henry [mailto:thehenrys at sympatico.ca]
Sent: Saturday, May 28, 2005 8:24 AM
To: calvinlc at earthlink.net; s-car-list at audifans.com; Matthew Russell
Cc: Wayne Dohnal
Subject: Re: [s-cars] Cruise control debugging

Calvin,

This is quite disconcerting... I was hoping to hear that you swapped in a
new Control Unit and everything worked!  The other thing that I thought it
might be are those switches on the brake and clutch pedals... it sure seems
like they might be the point of failure?

Since you have recent experience with swapping out the Control Unit, which
apparently is up in the passenger footwell somewhere?  Can you give me any
hints on how best to get at it?  I think I will give it a shot, since I have
another unit to swap in.

But now, that I think about it, the problem is more then likely a broken
wire that makes contact intermittantly.  Have you tested the signal that is
sent to the Control Unit from the turn signal switches?

Please let me know if you make any other progress on this issue.
Thanks,
Brent.
----- Original Message -----
From: <calvinlc at earthlink.net>
To: "Brent Henry" <thehenrys at sympatico.ca>; <s-car-list at audifans.com>;
"Matthew Russell" <skippertgore at msn.com>
Cc: "Wayne Dohnal" <wd1 at hevanet.com>
Sent: Saturday, May 28, 2005 9:56 AM
Subject: RE: [s-cars] Cruise control debugging

> Matt,
>
> I have the identical problem and I have spent well over 24 hours going
> through the Bentley procedure 2 or 3 times, taking the CC box apart,
putting
> in a 2 different CC boxes.  Everything on the Bentley checklist passes,
> argh!  I have even put the speedometer signal on the scope, set the cruise
> "manually" and seen the vasuum hold just fine, etc.  It is a very vexing
> problem.  Please let me know if you find any solutions and I will do the
> same.
>
> --Calvin
>
>
> -----Original Message-----
> From: s-car-list-bounces+calvinlc=earthlink.net at audifans.com
> [mailto:s-car-list-bounces+calvinlc=earthlink.net at audifans.com]On Behalf
> Of Brent Henry
> Sent: Monday, May 16, 2005 2:19 PM
> To: s-car-list at audifans.com; Matthew Russell
> Cc: Wayne Dohnal
> Subject: Re: [s-cars] Cruise control debugging
>
>
> Matthew,
>
> I have heard from another Audi mechanic, that all you need to do is ensure
> that the switch gets fully depressed by the arm of the brake pedal or
clutch
> pedal, without pushing the threads out of the mounting socket.  Even
though
> it does not require that the switch be fully depressed, this will allow
for
> incidental touches to those pedals without disengaging the cruise.
>
> Thanks,
> Brent.
> ----- Original Message -----
> From: "Matthew Russell" <skippertgore at msn.com>
> To: <s-car-list at audifans.com>
> Cc: "tim rad" <tr0910 at gmail.com>; <thehenrys at sympatico.ca>; "Wayne Dohnal"
> <wd1 at hevanet.com>
> Sent: Monday, May 16, 2005 1:16 PM
> Subject: Re: [s-cars] Cruise control debugging
>
>
> > Not sure about Wayne's symptom's prior to repair, but mine sure are the
> > same.
> >
> > I replaced the vacuum switches as well (didn't  realize that I could
> > just replace a 99 cent o-ring) and it has not cured this problem.  And
> > I'm in agreement that troubleshooting would be better (and cheaper)
> > than throwing parts at it.
> >
> > Bentley has a pretty detailed troubleshooting flowchart, which is high
> > on my priority list the next time my 13 month old daughter has a
> > playdate and I can spend a few hours in the garage.  First step is to
> > decide if it's an electrical or a vacuum problem, and proceed from
> > there.
> >
> > Anyone know how to correctly ADJUST these pedal switches?  When I
> > replaced mine, i simply counted how many turns they were seated in the
> > mounting bracket and installed the new ones the same number.
> >
> > But who knows if they were adjusted properly in the first place?
> > Bueller?
> >
> > -Matt, co
> > 92 s4
> >
> > On Monday, May 16, 2005, at 10:40  AM, s-car-list-request at audifans.com
> > wrote:
> > >
> > >
> > > Wayne, is your symptoms of cruise problems a gradual reduction in
> > > speed?  Mine is a sudden and unexplained shutdown, just like I had
> > > tapped on the brake pedal.  At that point the cruise will not resume
> > > or reset.  It seems like it is dead.  Perhaps 10 minutes later it
> > > might, or might not be functional again.  When it works, it may work
> > > for only 3 minutes, or it may work for over an hour.
> > >
> > > Tim
> > >
> > > On 5/15/05, Wayne Dohnal <wd1 at hevanet.com> wrote:
> > >> I agree with prior posts that suggested the highest probability cause
> > >> of
> > >> cruise control problems is the pedal switches, and this was the
> > >> problem when
> > >> my cruise control quit working.  It would be a waste of time and
> > >> money to
> > >> replace another component without checking this out first.  I
> > >> isolated my
> > >> problem by removing the windshield washer resivoir and cruise control
> > >> vacuum
> > >> pump.  I then "hot wired" the vacuum pump to open the throttle about
> > >> half
> > >> way.  At this point, if the throttle holds its position over time
> > >> then it
> > >> might be a control module or other electrical problem.  But most
> > >> likely the
> > >> throttle position , which you can easily see from up top, will slowly
> > >> close,
> > >> indicating a vacuum leak.  You can then isolate the leak one
> > >> component at a
> > >> time, but you may as well start with the pedal switches.  Just plug
> > >> the
> > >> hoses going to them, run the vacuum pump again, and see if the
> > >> problem is
> > >> temporarily fixed.
> > >>
> > >> If you don't mind a little micro-surgery, it's not that hard to open
> > >> up the
> > >> pedal switch and replace the o-ring, which will most likely fix the
> > >> problem.
> > >> I had a suitable o-ring in my junk collection, but I imagine it's
> > >> easily
> > >> available at a hardware store.
> > >>
> > >> Wayne Dohnal
> > >> 1994 S4
> >
>
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