Date: Tue, 17 Jul 2007 21:29:58 -0700
Reply-To: David Kao <dtkao0205@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Kao <dtkao0205@YAHOO.COM>
Subject: Re: electrical woes - new developments
In-Reply-To: <5D6A9D02-564E-4ED5-BFB0-48F5CA13F52D@mts.net>
Content-Type: text/plain; charset=iso-8859-1
Jeff, you just gave a good hint - tach bouncing all over the place.
The tachometer picks up a signal from the coil. This signal is really
a pulse at the frequency of the spark plugs firing. This signal has to
go through a signal conditioning analog circuit in the tachometer
before it is counted and covert the count into a voltage proportional
to the engine RPM. This voltage then drives the analog tachometer.
If the tachometer jumps all over the place it is getting very noisy
signal from the coil. The problem should have something to do with the
ignition. It is still not easy to pin point which part is doing it.
It can be the coil, the ignition module, the distributor (Hall generator
inside), wiring of the Hall generator to the ECU. Anyway, it is the signal
the tachometer picks up that is noisy causing the tachometer to jump
all over. The question is why it is noisy. Most likely it is a bad coil
or a bad Hall generator in the distributor or a bad ignition module.
If you have a 2nd Vanagon this would be a piece of cake. You can see
why some people have two or more. I have two. Some have over 20 all
kinds of vanagons. If you are in his neighborhood you would be in
good luck. So where are you?
David
--- Jeff Palmer <jpalmer@MTS.NET> wrote:
> So I got some great suggestions - maybe bad grounds, maybe bad
> alternator, try measuring the voltage across the terminals with the
> engine running . . .
>
> So I go out tonight and try and start it, and the battery indicator
> light reads poor, and it won't start. Turns over quickly, but won't
> catch. Yesterday when it did catch the tach was bouncing all over
> the place although the engine was running smoothly.
>
> The battery is relatively new, but I've never replaced the alternator
> or starter since I bought the van in 1993. Never had a reason to.
>
> Does this shed any light on the grounds vs. alternator theory? Or
> anything else?
>
> Thanks again
> Jeff
>
> On 15-Jul-07, at 4:54 PM, Jeff Palmer wrote:
>
> > Well, I'm 1600 emails behind with not much chance in catching up at
> > this point . . .
> >
> > So my 85 Westfalia seems to be running a little slow electrically-
> > speaking. Dash lights a little dimmer, windshield wipers a little
> > slower. Lately the CD player has even been cutting out when I hit
> > the brakes, headlights etc. (it will come back on within a second or
> > two).
> >
> > Any suggestions? Seems to start fine. I mean, as well as it ever
> > did.
> >
> > Thanks in advance
> > Jeff
> > 85 Westfalia
> > 69 notchback
> > 03 Beetle
>
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