[s-cars] Cruise control debugging

[tim rad]

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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