Date: Wed, 10 Aug 2016 13:15:29 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Intermittent low gauges
In-Reply-To: <CAHTkEu+S3kHk8=C+F-9whqBNSm0jyq6XruRPYud2GoZACBFbBg@mail.gmail.com>
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There are a number of common causes for these gauges to read low. They both get there power from a voltage regulator on the cluster itself. A bad connection on the pins or the heat sink (ground for same) can cause low voltage output. A bad round for the cluster and of course the foil itself.
Wide temperature swings based on load indicate a thermostat that is not in control or a cooling system that is saturated or otherwise defective. If outside temp doesn't change this much I would begin with the thermostat.
As for the low coolant warning system no scolding here but when the coolant loss is enough to prevent flow and pressurization of the system the gauge will also fail to indicate what is actually happening. Especially if the gauge sensor is on a plastic part or away from the head. At that point the gauge lets you know after you make enough steam and if your lucky you only blow some cooling system parts and maybe a head gasket. Cracked heads are usually the next step just before the burned valves and pistons. This is not a difficult or expensive circuit to fix.
Dennis
> Date: Wed, 10 Aug 2016 08:34:30 -0700
> From: dhanson928@GMAIL.COM
> Subject: Intermittent low gauges
> To: vanagon@GERRY.VANAGON.COM
>
> 84 chassis, Digifant inline in the diesel style..
> I have what I'm guessing is the stock instrument-pod in my inline VW
> van...no tach and no buzzers.... It just began showing lower than normal,
> and incorrect readings, twice yesterday on startup, both the fuel gauge
> and the coolant temperature gauge. Then they are right again.... Dunno if
> they creep back up, or correct themselves after the next start up.... can't
> safely watch their behavior long enough to see, but one episode they stayed
> low for a 50 mile trip... The fuel should have read full, but after just
> 35mi it was below the odd VW idea of 3/4 tank...and the temperature reading
> was just off dead cold when it normally reads just below the top of that
> two line zone they put at the left end...When loaded and flogging it, the
> temp gauge normally gets up to the led in the center. In cruise mode, this
> van indicates about halfway between the led and that lower, what must be
> the Teutonic warm-up zone...
> So both those gauges were reading too low for what was really there, in
> reality.... I double check the temp always with my oil temp and the
> alternator lite...
> My low coolant light has never worked...and before get "scolded" for
> that.... I don't care about that...
> Any how, is there a common ground, or perhaps an intermittent resistor
> that may be sometimes causing those two gauges to give lower than normal
> readings, and then be right again, sometimes? Thanks if anyone has any
> ideas..
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