On a long trip, just stopped working. Any ideas. Checked the fuse, all good.

 

VSS (Vehicle Speed Sensor). It's a long black sensor that looks like a dipstick. It plugs into the transfer case underneath the oil filter side. It's so easy it gets easily complicated. You don't even need tools. It has a lever type tab that you push down and turn and it pops right out. They're cheap too.

You don't have any of your specs in your sig, so I'm going by what I have and how to fix it.

Here:

Vehicle Speed Sensor SC346 For 1996-2004 Audi A4 Quattro A6 Quattro A8 Quattro | eBay

 

Is there a vcds sensor to check if it's working? My cruise control hasn't worked ever and I figured it was an expensive fix so I never worried about it, but if it's a $10 sensor, I'll definitely do that.

 

I was in the exact same position. I spend hundreds, replacing sensors that were perfectly fine and had nothing to do with the problem. I almost did some "soldering fix" that I saw, where you actually open the module up and solder the board, but (through the help of someone on here), I found out that it's just that one sensor. Super cheap, super easy (you don't even need tools) and 100% effective. That's what goes bad. Not 100 expensive parts. I replaced mine for $7-$10 bucks (in less than 5 minutes) and it's worked perfectly ever since.

 

Was your speedometer off? Throwing irrational speeds and whatnot? Seems this sensor is supposed to fix that, but as a secondary can fix cruise control.

As far as I can tell, there's 6 things that can cause CC issues (on 2.8's):

Fuses #5 or #31
The stalk
The CC module
The actuator
This VSS
A vaccuum leak

From research, the cc module is the most likely culprit, and I see where the soldering fix you mentioned came from. The stalk is the other popular fix but also the most expensive.

I really doubt mine is a vaccuum leak as I spent quite a bit of time making sure there were none from a different issue. Also the fuses take 30 seconds to check so it's unlikely those.

I'll get around to checking this but I've got a power steering issue at the moment (just needs a new pump ) as well as a timing belt due sometime this spring.

 

Do the sensor first. It's cheap, easy and most likely the source of your issues.

 

Fortunately for me the solder fix you were talking about (since it was free) fixed my issue. I also did the turn-off-and-on-the-switches-on-the-stalk-1000-times-quickly, so it could have been that too.

 

Awesome. Glad I could help.

 

Thanks for the responses. I'm trying to work out if I have the vacuum system or the electronic system. My car is a '98 model so I assumed I had the vacuum system but there are two lines coming from the throttle. One I assume is the accelerator input, the other goes to a box marked 'Cruise Control' which has a wiring loom coming out the other end. I've attached photos below, does this mean my cruise control is not a vacuum system, but the other one?

 

In the end, I ended up finding the set wire from my aftermarket cruise control and wiring a new switch into the dash. So looks like the problem was the set switch in the stalk. When I tested the set switch in the stalk with a multimeter, it gave intermittent results.