Cruise control won't hold

[Algernon]

Cruise control works but doesn't hold the speed. The car just gets gradually slower.
I searched and found something about a diaphragm tearing in the clutch pedal switch.
Is this likely to be the problem or possibly one of them? My first option?

[Zoig]

I have the same problem with my UrS6, i suspect the air/vacum system, becuase the speed is getting gradually slower, instead of not fixing at all or suddenly dropping. For me this looks like piping problem and the pump can not keep up with the leaks or the pump is too weak to suck the air out of the system. Either way, i'd start looking from the air system.

[irishs2]

I have the same problem on the avant,



Might be a leak on the vacuum system and as you said could be either of the vacuum switches for brake and clutch pedals .You could disconnect and block one vacuum line in turn and see if the problem goes away.

More info in this thread

http://www.s2forum.com/forum/showthread.php?t=26221

[Andriux]

first,try to clean vaacum compresor (Nr8)

[bertman]

Had exactly the same problem,but i have manage to cure it and now works better than ever.
you shouldn't get leaks on the vacuum hoses unless they are loose or have been rubbing.There are plenty of btdt on the forum.I just went over the whole system,checked the pedal switches,cleaned contacts and checked vacuum lines.I wired up the pump to a power source and that worked fine,then looked at the bellows which I removed pushed down and then put my finger over the hole..it didnt leak.
The final thing I did was gently with a small screw driver opened up the side of the indicator stalk and sprayed alot of wd40 down it,then moved all the cc switches around went for a test run and bingo,the cc came on and stayed onNo more gently dying on me.
There is a good write up on 20v.org,look at that for test procedures on the cc system.
Do not really know exactly what cured it but I would say freeing up the stalk played a part

[Andriux]

http://www.humanspeakers.com/audi/cruise.htm

[EBR]

I had this on my car, the switches for the clutch and brake were just leaking a little, new O-rings cured it!

[mallster]

Yeah have had problems with previous audi's if there is any problem with the brakes i.e abs sensor even a sticky caliper can put the cruise control out.
hope you get it sorted mate

[Håkono]

I have a problem with my retrofitted cruisecontrol (RS2).
All the wires is correct fitted (i think):
ground-chassi
white/blue-speed signal
Blue/black-ignition 12v
Red/black-breaklight red/black (is this normally 0V and 12V when hitting brake pedal?)

Both of the switches to break and clutchpedal is adjusted and no vaccumleak in the hooses.

The ECU is in order (tried 2 pieces).

The problem is that it won't hold at all. When i set the cruisecontrol i feel the pedal holds in 1 sec but drops immediately.

When i set the cruisecontroll i have no voltage over the ventile in the vaccumpump. Because of that the vaccum drops i think. The ventile should have 12V while the cruisecontrol is ON??

Any ideas what is wrong?

[Håkono]

Is this wire (red ring on picture) connected to the red/black wire on the brake light switch? This red/black wire out of brake light switch is normally 0V but turns into 12V when hitting brakepedal. Is this correct?