[s-cars] Cruise control debugging

[Matthew Russell]

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