Re: Cruise Control Troubleshooting

[Sandy Duffy <sandy@pcnet.com>]

At 12:50 PM 11/8/97 -0500, you wrote:
>Problem: My 91 200q has intermittent cruise control problems.  Sometimes
>(not very often) it turns on and operates normally. Most time it doesn't
>SET at all.
>
>This all occurred after replacing the crankcase breather hose, and multiple
>coolant hoses. I was wrestling with all sorts of stuff behind the block and
>on the side of it.
>
>So I started troubleshooting, I thought it would be a vacuum line. Replace
>the one from the cruise control diaphragm to the "t" connector and that one
>to the vacuum pump. Also checked for vacuum leaks, couldn't find any
>upstream of the "t" connector. The diaphragm should be ok.
>
>Next step is to do some simple electrical checking of components from the
>"brain", but it's under the dash panel above the glove box, don't want to
>go there.....
>
>I'm thinking for some reason it's the vacuum pump, either mechanically it
>is workingintermetintelyy or it must have some kind of valve that
>opens/closes when you turn the cruise control on/off to dump the vacuum. If
>so, I'm thinking it's not mechanically working. 
>
>Any BTDT's???
>
>TIA
>
>Paul
>
>
>*********************************************
>Paul Waterloo
>Brookfield, IL

Paul:

I think you are looking too far into the cruise system as this may not be an Audi-god-appeasing problem!  The cruise control has a switch on the brake pedal and on the clutch pedal (if you have one) that will turn the cruise control off if either one is depressed.  The point at which the circuit opens is adjustable via a pair of nuts that hold the switch against the pedal lever.  Commonly, one needs to readjust the switch point as components age.  The fact that you cruise control will work sometimes indicates that it is probably good.  One way to test to see if the switch needs adjustment is to pull the pedals up to the top of their range with you big toe under the actuating levers and then see if the cruise control works.  If it does all you need to do is readjust the cut out point of the offending  pedal.

HTH

Sandy