[T3] Fuel Gauge [was Progress Thanks to P.A.]

[Jim Adney]

On 31 May 2011 at 9:30, Bryon Garvin wrote:

> This reply reminds me of something I meant to ask.  Jim fixed my fuel sender
> unit and all has been well for months.  However recently, I noticed that the
> gauge will sometimes display completely different values from one drive to
> the next.  I found that tapping on the gauge will settle the needle back to
> where I was expecting it to be.
> 
> Is this a grounding issue at the gauge, an internal issue with the gauge, or
> just how these gauges have always worked ;)  ?

I THINK it's probably a grounding issue. When this is happening, does 
the needle twitch when the turn signals are blinking? If so, it's the 
grounding of the gauge.

This area has always puzzled me, because I've seen grounding problems 
there. on my own cars, that were cured by seating the gauge properly. 
Yet, I just went downstairs to look at a gauge and its rear bulb 
holder, and I see that there is a term 31 there, for a ground wire. 
That wired ground should make the spring clip ground unnecessary.  

The wired ground is passed on to the gauge body by the lower of the 3 
brass pins that lock the 2 halves together. A bad connection there 
would make the spring clip the only ground for the gas gauge. It's 
not clear why, but the gas gauge is actually a 3 terminal device, and 
it requires the metal gauge body to be grounded..

So, maybe what you should do is reach up behind the dash and just 
pull the rear base off the gauge and then reinstall it. That may 
refresh the connection.

I don't think I have any pre-'69 bases here, so all of mine have that 
term 31 on the back. Does anyone have an early base that they can 
look at to see if there is no term 31 on it?

Checking the microfilm, I see that the latest bulb holder is the B 
version, so it's quite possible that there was at least one earlier 
version that did not have a ground. Does anyone know what other 
change might have occurred that gets us up to a B version?

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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