Bert.Otten@nni.nl wrote:
>But apart from this slight nuisance ;-) , I encountered some other
>thing. When the engine revs above, say 4000 rpm, the tach starts to
>swing wildly up and down sometimes reaching 0 and then again to 6000
>rpm.
Unfortunate past experiences in my 77B have led me to hypothesize that
the Psychotic Tachometer Syndrome (PTS) is a sign that the alternator is
just about fried; probably something to do with intermittent currents or
big changes in voltage. Every time I've observed PTS in my car, the
alternator stops functioning within a few days, and PTS doesn't return
after installation of a freshly rebuilt unit. Your car with a known
shot generator lends some support to this theory. See if it doesn't go
away with a new generator.
My tach also does some a similar number when I shut the car off while
the cooling fans are going. It kicks from idle up to about 3000 RPM
while the fans are spinning down. I think in that case, after cutting
power to the fans they actually start working as DC generators, feeding
current back into the system. There's a less pronounced effect with the
heater fan. Fortunately that doesn't seem to be doing any damage to
anything.
--
Jay Tilton | jtilton@vt.edu
|