cruise control antics

Alex Kowalski akowalsk at
Mon Jan 10 22:53:15 EST 2005

> as soon as terrain changes, speed jumps alarmingly; it seems to be 
> maintaining throttle instead of speed.

OK just a first crack at it...why would the control unit allow the system
to hold vacuum (constant throttle opening) and then fail to
respond to an *increase* in speed, in which case it should interpret the speed increase 
(from the instrument cluster) properly and bleed off the CC system vacuum to close the throttle?

I am guessing the CC control unit has gone flaky.  Tapping brake/clutch
*must* deactivate the cruise through another set of terminals and by
bleeding off vacuum.  But since your cruise doesn't respond to the switch OFF command after being set, 
it sounds like the control unit has developed a mind of its own after it's turned on and set.

Also, isn't there a little bleed-off valve in the pump assembly someplace to regulate this? 

These are pure conjectures, I'm waiting to hear more authoritative ideas...


> Message: 11
> Date: Mon, 10 Jan 2005 21:48:23 -0500
> From: Brett Dikeman <quattro at>
> Subject: cruise control antics
> To: quattro at
> Message-ID: <41E33E77.300 at>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> The 200q20v has a new trick- unintended cruise control acceleration.  I 
> discovered this for the first time in a couple months coming home late 
> from work and just wanting to do a nice easy cruise home.  I'm pretty 
> sure cruise control worked fine back in October for my trip to Mont 
> Tremblant.
> I'll set cruise control, and it will maintain throttle for that speed, 
> but as soon as terrain changes, speed jumps alarmingly; it seems to be 
> maintaining throttle instead of speed.  Also- tapping the brake or 
> clutch pedal WILL disengage cruise control (counterindicating a problem 
> with the linkage or vacuum line, and obviously the vent switches work), 
> but the cruise on/off switch will NOT turn off cruise control (yipes!).
>   Further- in the off position cruise control can NOT be set (ie by 
> pushing the stalk button for ACCEL), which seems to counter-indicate a 
> shorted switch.
> I'm baffled; never experienced nor heard of this kind of 'failure', and 
> I've got some conflicting symptoms.  Any ideas?
> Brett
> -- 
> "They that give up essential liberty to obtain temporary
> safety deserve neither liberty nor safety." - Ben Franklin
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