[urq] tach failure

[Ed Kellock]

So what happened to "Kahleefornia"?


On Thu, 7 Oct 2004 09:53:47 -0700, Buchholz, Steven
<steven.buchholz at kla-tencor.com> wrote:
> ... my wife and I frustrate each other from time to time because
> whenever there is an electrical connection problem on something she says
> it must be "shorting" ... I try to explain to her that a "short" is a
> very specific condition, one that in fact is rare in situations like
> this ... and for many reasons is good that it is rare.  Sorry about the
> rant ... I would say the situation would probably be better described as
> an "opening" ... ;-)
> 
> You've got some sort of electrical connection problem going on.  A tach
> is a very simple device in terms of its interface, it gets power, ground
> and the tach signal from the coil.  If the tach quits working the
> problem is a connection issue on one of these inputs or the tach itself
> is bad.  Given that you seem to be experiencing other electrical issues,
> I'd guess that the tach is OK.  Unfortunately, most electrical
> connection problems are intermittent, and so the process of opening up
> the area to investigate may fix the problem.  Fortunately, on the urq
> you can get access to the IC without having to move it much ... pull the
> cover off, but leave the IC in place and attached.  Start the engine and
> see if the tach is working.  If it is you might want to try wiggling the
> wires a bit to see if you can't make it fail.  Assuming you can make it
> fail, measure power and ground at the tach to see if one or the other is
> missing.  You can check for the tach pulses with an external tachometer
> ...
> 
> Before I dig in too far on a troubleshooting session like this the first
> thing I do is to collect the information about the various odd behaviors
> and look at the related circuits in the wiring diagram to see if there
> are any common threads.  I would recommend that you do this.  Be as
> specific as you can in terms of the observations you've made ... and
> also see if you can repeat  them ...
> 
> Recently I've had a couple instrument cluster issues that turned out to
> be connection problems in the flexible circuit board that provides the
> wiring for the instrument panel.  Unfortunately it is very difficult to
> identify hairline fractures and such.  I think this is probably where
> your time will be best spent ...
> 
> Steve B
> San Jose, CA (USA)
> Perhaps I should start calling myself West Coast Steve?  ;-)
> >
> > Occasionally my tach just dies.  Sometimes I would start the
> > car and have no tach and re-start would solve it.   Sometimes
> > I'd be tach-less for a couple weeks then one day it would
> > come back.  Now I've noticed that on the rare occasion I honk
> > the horn, the tach can die.  Ditto headlights...or is it
> > brights.....can't remember.
> >
> > Seems like it's shorting???
> >
> > So I plan to get inside the IC (not the intercooler) this
> > weekend...what do I look for (besides a new tach!)????
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