Re: Funny Tach Movement (whatsit mean?)

[Jason <jason@scirocco.org>]

At 02:05 PM 8/28/98 -0400, Peter Walsh wrote:
>Hey All... I have a question.  The other day on my way down to NC I got
>stuck in hellacious traffic.  A few times I was stopped for a few min at
>a time and shut my engine off to let it cool (at times it got up to 120
>Cels)  and If I put the car in the ON position (w/o turning it over) the
>tach would go from 0-8 and sort of bounce back.  (engine not on).
>
>What does this mean?  Did it have to do w/ my engine hot?

My 87 16v does the same thing... and it's always when the engine's hot.
Generally it's when I'm in traffic, and it seems to be related to the
temperature under the hood rather than the water or oil temperature.  
	Someone else just posted to the list about this happening while the car
was idling (I just glanced at the post quickly)... mine also does that.  If
it's very hot under the hood, it will bounce up real quick and then return
to normal- the first couple times it did it I thought I was seeing things
out of the corner of my eye.
	The easiest way to make it do it is to barely touch the gas pedal while
you're sitting in traffic for a while in the heat.  Tripping the idle
microswitch when it's really hot under there will generally make mine do
it.  Or, the other way is to turn the car off; and then each time you
switch the ignition on, it will do a 0-8000 and back.  If it's really hot
under there, the tach will bounce up and down as the engine turns over; the
more resistance, the higher the rpm displayed- so as the engine's turning,
the tach will bounce between 2000 and 4000, bouncing in unison with the
starter's pitch.
	I just got a new thermoswitch for my cooling fan from Mark in the mail the
other day, and I will be replacing it in the coming days.  I've realized
that it gets way, WAY, *WAY* too hot under my hood.  I sat in 95'F traffic
for four hours last week and actually boiled the water in the battery as
well as the windshield washer fluid.  It's *THAT* hot under there.  (In
case you're wondering, I had to buy a new windshield washer pump and
battery that afternoon.)
	As silly as it sounds, if you're having trouble with temps that high under
your hood, get a new switch, but in the meantime, you can cool things down
ironically by turning on the A/C, because it forces the cooling fan to go
on high.  It's worked wonders for me.
		Good luck- and don't worry too much about it!
				Jason


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