Troubleshooting Passat Cruise Control

Dear reader,

I live in Australia and have a 1998 VW Passat wagon which has now done over 120,000km but which I want to keep as being well looked after, it is cosmetically and I though, in good mechanical condition.

However not long ago I went through the painful and potentially costly experience of identifying and fixing a faulty ABS indication on the dash.

I refused Volkswagen's solution of simply replacing the ABS Hyrdraulic Block at cost of almost AUD 3000 plus labour (!) and at first began trawling eBay and later the Internet for information generally and finally understood I could have the ABS electronic module rebuilt in Australia for just one tenth of the price and today still resent or mistrust Volkswagen for not telling me this was another option. They still say they didn't know it was.

Anyway I am now tackling the sometimes functioning but more often than not, non-functioning cruise control.

I don;t know why after my ABS experience but I trusted Volkswagen again to diagnose the problem. They had the car for three days, tried replacing the brake light switch and returned the car as 'requiring further diagnosis so I have again turned to the Internet and came across this thread (http://www.automotiveforums.com/vbulletin/showthread.php?t=148649)and the contribution below:

The most comon cause of cruise failure on Passats is the vacuum vent valve on the brake pedal (and clutch if applicable). The switches are both electrical and vacuum. The vacuum vent seal will begin to leak & causes intermittent failure to engage or loss of speed on hills. Sometimes you can help them along by readjusting or pulling up on the pedal, but eventually they need to be replaced.

This best describes the behaviour I have observed and wonder if anyone can offer the benefit of their experience?

If so, I can confirm that the cruise control did not work or rarely worked before and pulling the brake pedal up has caused the cruise control to work again although I don't know yet for how long.

But there is no sign of the yellow dash indication which used to appear before.

Also I found out this morning and interestingly AFTER needing to pull the brake pedal up for the cruise control to work that in addition to the brake light switch VW also replaced the vacuum vent valve or part no. V811907343B. At least they say they did and I see now it's on the invoice which I haven't yet paid.

Two things, what might a) the cruise control working but not the dash light and b) needing to pull the brake pedal up if the vacuum vent valve has already been replaced mean and what steps should I try next?

Should I for example, remove and send the cruise control module away for tesing and is possible, rebuilding? Or could it be corroded wiring as I have read in other threds or does the cruise control working intermittently rule this out?

I have for example, a reply from ATE (Auto & Truck Electronics) who it would seem many people in the US send their modules for testing. I have cut and pasted their email below but obviously would prefer to send it somewhere in Australia but don't if for example, the people who tested and rebuilt my ABS ECM know about the "known failures" desribed below.

Thank you for your interest and time. Any reply is much, much appreciated.

Sincerely,

David Morgan

Auto & Truck Electronics
We can rebuild your cruise controller, with updates, we correct failures and known future failures we have 1 to 2 business day turn around service, we Include our 3 year warranty, your rebuild cost is $99.00 U.S. I have attached our R&R form please complete & include this form in package. Return shipping to Australia via United States Postal Service is $38, 3 to 5 days return service,We accept International Western Union.

There is a clutch vent valve for the cruise also ifyou have a manual transmission.
I most commonly see the cruise modules go bad on theese b5 passats. Check ebay and www.vwvortex.com

There is a clutch vent valve for the cruise also ifyou have a manual transmission.
I most commonly see the cruise modules go bad on theese b5 passats. Check ebay and www.vwvortex.com (http://www.vwvortex.com)
Thank you Veedub for your reply,

Well, here's a summary.

Volkswagen had the car for three days and say they replaced a brake light switch and (I found out later) the brake vacuum vent valve but gave it back to me a few days ago as 'requiring further diagnosis'.

Just aside, I read somewhere in another thread that Volkswagen generally don't want to know your car after 75,000 and this has been my experience. Or at least they are not interested in affordable repairs for example, at 120,000 their only solution to repair a faulty ABS code was to replace the whole unit for AUD3000 plus labour. And this they said was a discounted part price!. After much research on the web I went from trawling eBay in Germany for a second hand unit to realising I could have just the electronic module tested and rebuilt in Australia which ultimately I did and fixed the problem for a 1/10 the price. Volkswagen didn't tell me this or offer it and say they didn;t know it was even an option!

So I don't know why I trusted Volkswagen to diagnose and fix the cruise control - yes, I do, they had to fix the bonnet catch poperly which they hadn't when they replaced the timing belt and I asked them to have a 'quick' look only.

Anyway, the new brake light switch and vacuum vent valve in themselves didn't fix the cruise but after reading about it somewhere here pulling the brake pedal up, did!

BUT only it would seem for about 24 hours. Last night the cruise control was again not working and pulling up on the brake pedal made no difference.

While the cruise was working though the little yellow dash light indicator I thought used to illimuninate while engaged, would not illuminate. But in hindsight the light might be my imagination or impression from another car because I can't find any reference to one in the owner's manual.

So given above the would you agree the odds remain with the cruise controller being faulty and do you know if a 1998 Passat had a cruise control dash light?

If so, then I have the instructions to remove and send the controller to ATE in the US (a long way from Australia). Would you recommend anything else?

Thanks again,

Dave Down Under

PS The vehicle has Tiptronic transmission so I guess that's not considered a manual.

The brake switch and vent valve are adjustable. The installer needs to set the 0 position on them. THey screw in and out, and if you had to pull up slightly on the brake pedal for the cruise to work it would only lead me to believe the switch was not adjusted properly. The dealer has a pin-out test box of which they plug into the cruise module and they can test every operating part of the cruise system. It should only take approx 1/2hr to diagnose what part is faulty unless its a broken vacuum line or something you need to search into. I most commonly see cruise modules fail on theese if the cruise just doesnt work at all. If it works intermittently than it would be more related to the vacuum system. But if your module was going bad and is now bad it would have worked intermittently for a while than just stopped completely. Without the test box I cant really help other than give suggestions.

Hi veedubmechanic,

Thanks for your reply above.

The two conclusions you reach help make sense of what I (we) do know.

Although it may have as you suggest failed completely because the cruise controller worked recently albeit after pulling the brake pedal up I agree that the preimse should be:
The vacuum vent valve (fitted by Volkswagen) might need adjusting before
Removing and sending the cruise controller away to be tested and if possible, rebuilt.Personally I'd just as soon go straight to removing and sending the controller away however as I haven't yet found anywhere in Australia who have experience with andare confident about fixing European cruise controllers, I'd have to send it to the ATE in the US which is it would seem where most people send their controllers.

So I ideally I need to determine first if the valve replaced by Volkswagen has also been adjusted.

However because it's construed as interference I can't ask Volkswagen. But what can I do! They had the car for three days and returned it without fixing it and 'requiring further diagnosis' after replacing two switches (invoiced) and they say, six hours which have not been invoiced. They just seem to want to take their round about way of doing things which I can't afford. If they have already spent 6 hours God knows how much I'll be up for if they actually fix it!

And what bugs me is, I thought these modern vehicles had as you say, plug-in computers to diagnose problems relatively quickly.

Is there any way I can determine whether the valve has been adjusted or adjust it myself before I resort to removing and sending the controller away?

Cheers,

Dave Down Under