Cruise control problem

[veedbya]

my 98 wolfsburg ed (A3) cruise control only works occasionally. I have the service manual and did everything suggested in the troubleshooting section with the exception of checking the speed sensor. I never got around to getting someone else to spin the tires while I watch a voltmeter. Has anyone else had a problem with their cruise control??

[boschmann]

I find the manuals aren't too good at describung checks of the vaccum system, they just say check it then go on to electrical checks. Did you find that the brake (& clutch if applicable) pedal switch holds vacuum? You can pull the hose at the pump that runs to the pedals & pull vacuum with your mouth. Often the plastic hose under the dash will leak. Here's a link to a guy that has a different approach:

http://www.gti-vr6.net/library/elect...rol.html#mark0

[veedbya]

I checked all of the vacuum hoses and vent valves, they all hold. After testing the speed sensor, I bought an ECU (used) hoping that may be the problem but still nothing. With all of the playing around I have done, it managed to work several times within the past week, but it seems to be dead again now. When it worked, I heard a click as soon as I pushed the set button, but no click when it doesn't work. I don't know what that means...
It is driving me crazy though!!!!

[boschmann]

Is that the cruise control module you replaced? Do you hear the vacuum pump come on? It it manual or automatic? Which engine?

[veedbya]

yes, the cruise control module is what I replaced. I didn't hear the vacuum pump come on (except when I did the test on it). It's a manual, 2.0L.

With all of the tests, everything works and I can't believe that both of the CC modules I now have are shot which makes me wonder what else is there??

[boschmann]

Are you performing the tests with a VW VAG 1466/8 tester? I'm unsure what manual you are using & what tests you've performed. Basically theres just power from the control switch in each position, brake & clutch switches (electrical part) vacuum pump, & speed sensor. When you ran the pump manually did the throttle open fully & if you hit the brake did it close back? That would eliminate vacuum leaks. The pump is the only thing I can think of that would make a click, but if it's not running some of the time it really could still be any part of the system at fault. It would point to electrical though as the pump would always run if it were a vacuum problem.

[veedbya]

I have been using the Bentley manual with a multimeter. I have performed all of the tests in Bentley and it passes all tests. It isn't a vacuum leak either, because after running the pump and letting the throttle go to the floor, I waited about 5 minutes with the pump off and the throttle stayed open fully.
Is there any way that the engine being on under normal driving conditions would affect the cruise since it passes the tests with the engine off?

[boschmann]

As long as it passed the switch & sensor tests (some should be done with key on) I can't see how that would make a difference. Perhaps you can find another module, they should have at least a 30 day warranty on the used one. Try this site;

http://www.car-part.com