[urq] A4 content

[W. Bremer]

Forgive the A4 content, my urq is resting is a heated garage for the winter, so I get to play with my daily drivers....  

For you A4/A6 owners out there, any thoughts, comments, opinions???

Over the past 5 months, my 1998 1.8T A4 with Tiptronic (now with 68K miles), has suffered from erratic cruise control behavior:  It would not engage, or if it did, it would self-disengage without warning after 5 or 10 minutes.  When it would engage (from pressing the "set" button), I could hear the faint "click" sound from the control module above the glove box.  With the help of Bill Bennett and the Bentley A4 CD, I checked out the various systems as best I could (without pulling the air-bag steering wheel to check the switch in detail) to see if I could find an obvious problem.  I checked all the connections for contact and cleanliness, and also circuit continuity for those I could access, and sprayed some electrical contact cleaner stuff into the cruise switch on the stalk, etc., etc., to no avail.  I even opened up the control module looking for bad solder or a burnt component).  Sometimes it would work briefly, but most often I could press the "set" button on the stalk but the control module would not engage the system.  The two brake slight switches were firmly mounted and held vacuum or controlled the electrical circuit correctly.  Following Bentley, I confirmed that the hose and actuator vacuum system held a vacuum.  In a nutshell, I was unable to reliably get the system to engage under all sorts of speed and button-pushing situations.

Yesterday evening, in the -10F temp, the car's battery was too weak to spin the starter fast enough to start the motor, so my wife got a "battery boost" from the security folks where she works.  Whether from a big drop in voltage (from then initial cranking effort) or a voltage spike from the successful jump start, two things happened: (1) the radio went into "SAFE" mode, easily corrected, and (B) today (in +4F temps), over the course of 2.5 hours of highway and local driving, the cruise control performed flawlessly, even as I deliberately mucked with it to see if I could get it to fail under controlled circumstances.  (In the past, such "mucking" (disengaging, re-engaging, resetting with new speeds, etc.) guaranteed a non-functioning cruise system.

My suspicion is that the voltage drop or possible spike somehow affected something (presumably the control module).  Has anybody else experienced this sort of cruise control behavior?    Any thoughts as to what might have been causing the recent system failure?

Thanks, 
Bill
'82 urq
'85 4KQ
'86 5KCSTQ
98 1.8T A4