I have a 98 Audi A4 1.8 with 5-speed that I purchased recently for a private party. The cruise was working but would release at times when going up hill or meeting a semi, etc. Now it doesn't work. It seemed before that there was possibly a loose connection with movement of the lever forward/backward (bright/dim control). Anyone had this experience and is it probably the servo unit?? or control for the cruise? Any suggestions or advise would be appreciative. I hate driving out on the road without it!! Thanks!

 

Could be switch or could be the speed sensor. If you have access to a vagcom, you can check for codes which will tell you the problem.

If not, you can try to clean the switch with some TV tuner cleaner available from radio shack for about 10 dollars. Unfortunately, most of the cleaner doesn't reach the contacts. You can try however. If that doesn't work and there is no code with a VAGCOM (note these would not show up on a plain OBDII reader), there was an instruction on audiworld, I believe on how to disassemble the switch and clean it.

 

Can a vacuum leak screw with our cruise control? I know some cruise is vacuum controlled.

 

'98 A4 1.8T apr chiped

I have been through the cruise control system with the help of bently manuals and here is where I have learned and what I still don't know.

First, the vacuum system for the engine is independant from the vacuum system for the cruise controll. I have tested the cruise vacuum pump and vacuum release vavle inside of the pump. Energizing the release vavle shut it (to build vacuum) and entergizing the pump of course creates a vacuum (up to about .1bar, carefull this will rev a running engine past 4000 rpms!) that pulls the throttle. That works, then I checked the clutch and brake peddle vacuum release valves (also connected to the respective electrical switchs) and they release vacuum when slightly depressed. That means the vacuum portion is ok. Next I used the manual to test the electrical switches in the cruise control stick, clutch and brake. I tested these switches at the connector to the cruise control module with the volt meter on the ground pin and the pin to the respective switches. These all turned off or on at the appropriate time. The brake peddle switch wasn't stricktly "on" or "off". There was a progressive drop in voltage over a short initial travel of the brake peddle. That all seems to work well enough. Then I was able to record the pulse signal from the speedometer at the plug for the cruise module and verify power. With all of the power, switches and speed signal comming in the only component left was the moduel itself. So I ordered a used control module from a junk yard. The "new" module didn't work either. I believe there are three remaining possibilities: one, both modules are broken, two, a wire in the manual isn't correctly defined, three, I have missed something. I am hoping that I have missed something! I will be sending back the "new" control module for exchange of "newer" unit.

I saw a posting somewhere about control module location. It is behind the glove box. Simply reach between the dash and the top of the glove box door to push the two springs back. The door will drop down and hang on the hing!

hope this helps the trouble shooting.

 

If you need to replace that switch it will be about $140. You can get it from ECS Tuning (Cheapest I've Found) at the following link:

ECS Tuning

Then you can replace it with the following instructions:

http://www.audiworld.com/tech/elec92.shtml