[T3] fuel gauge and gauge light fluctuating

David Yaghoubian goob at roadrunner.com
Mon Sep 22 03:43:53 PDT 2014


Responding in order of Jim's previous reply:

-After seeing that the gauges are virtually identical in dimensions, the
fitting issue seems to be that I can't push the gauge far enough forward to
get the clips to seat behind the dash due to too much thickness in the
replacement pad. I can probably razor and/or Dremel that inner pad rim down
to get the gauge in far enough to get the clip ends past the dash and obtain
a snug fit, but before doing that I wanted to try to make sure it wasn't an
issue with the lamp base, which it doesn't seem to be.

-By "tap out" I meant the gauge would max out, sorry. Which leads to a
revelation I suddenly had. Because I was driving relatively far when I
noticed the issue beginning the other night, I wasn't sure how much gas I
had in the tank. Long story short, I thought I had about a half tank, where
as it turns out I was near empty. Three gallons of super I had on hand in
the garage were sufficient to prove the "wait, I'm lame because I don't know
how much I actually have in the tank and the gauge might actually not be
malfunctioning all the time" hypothesis. Hence, some (but not all) of the
bogus readings were in fact accurate... so the fuel gauge is still iffy, but
not totally malfunctioning.

-In taking steel wool to the outside of the gauge body, and a file to the
inside edge of the gauge hole in the dash, I now have a relatively reliable
fuel gauge, and lights that are intermittent with a slap on the dash. If I
push on one edge or the other, the condition where the fuel gauge maxes out
hard and/or drops to empty occurs, and the gauge lights flicker on and off.
While this doesn't really explain why this problem is occurring all of the
sudden where it hadn't for the ~6 years since I put in that gauge, it seems
to be a no brainer at his point (and please, correct me if I am wrong/don't
have a brain ;) that I either need to modify my replacement dash pad to
enable the fuel gauge clips to seat behind the dash (thus making a solid
ground) OR install the other lamp base with the #31 ground post. Unless
there is any sense in doing both? According to Jim's response, the answer to
this seems to be a clear no.  

-Re. which of the two routes to go since they would be redundant, my concern
in modifying the pad would be cutting too much material so the gauge was
loose. This isn't  likely because I am not that lame, but stuff happens as
we all know. Or that I would do that mod and the condition would be the
same. My concern in swapping out the lamp base would be the potential for
the extra base I have to not be functioning correctly for whatever reason,
making that a total waste of time and potentially causing other wiring
problems. Hmmmm.....I'm kinda torn on which to do. Has anyone ever
encountered a bad base? This one looks to be in good shape, but I have never
tested it. Any strong arguments in favor of one solution over the other?
Doing both? 

-Last thing I would like to understand better if possible is why the fuel
gauge ground post/terminal and lead is insufficient itself for the gauge,
necessitating the dash contact and/or the #31 ground post addition. Like, in
my stock 68 with no #31, why the ground post at the rear as well as the
necessity for the dash ground... which did work, but ultimately led to the
determination that still another ground wire was necessary? Third time's the
charm? ;)

Thanks again!

Dave
68 Sqbk

-----Original Message-----
From: type3-vwtype3.org [mailto:type3-vwtype3.org-bounces at lists.vwtype3.org]
On Behalf Of Jim Adney
Sent: Sunday, September 21, 2014 3:10 PM
To: type3 at vwtype3.org
Subject: Re: [T3] fuel gauge and gauge light fluctuating

On 21 Sep 2014 at 12:34, David Yaghoubian wrote:

> So to start, I pulled the gauge back out and confirmed that my lamp 
> base (which I was calling a harness for lack of appropriate term) does 
> NOT have the #31 ground tab on the back. I think it is perhaps 
> important to mention now that I installed a '71 gauge set when I did 
> the dash in 2006 (to get the trip odo primarily) so I am running a 71 
> gauge without a #31 ground. Again, this hasn't been an issue up until 
> last night (although I don't know if this has to do with why I can't 
> get the gauge to seat fully)

Thanks for the clarifying that the #31 tab must have started in '69. 
Before that, the only ground was via the retaining spring clips. '71 and
'68 gauge heads should fit exactly alike, so I don't know why yours doesn't
want to fit all the way on. Since you seem to have 2 of each parts, see if
you can figure out what is interfering, or if they are together as far as
they are supposed to be.

> Right now, if I push slightly on the left rim of the gauge, the lights 
> come on full in the gauge but the fuel gauge needle reads dead empty. 
> When I release pressure from that edge, move the gauge a bit, or tap 
> the dash just above it, the fuel needle taps out, and the lights go off
completely.

What does "taps out" mean? Full lights should mean a good ground. I agree
that this is confusing.
 
> Regarding adding a #31 wire myself, I will go back out and take a look 
> at the wires joined to the socket just below the hole where the black 
> wire comes in (those would all be grounds, correct?) and see if that 
> is something I think I can handle without melting anything. If not, 
> perhaps I can purchase one of your extras Jim?

I'll be happy to sell you one, but you found one there. You might find it
easier to solder in a new wire than to undo all the wires and get them
hooked back up to the right places.

> In absence of a #31 wire for now, is there a way to definitively tell 
> if this is a ground issue at the housing before getting into the 
> soldering or swapping out what was a perfectly functioning lamp base?

Not at all clear. My first thought was that this was simple, but your
symptoms seem to point to additional problems. I guess at this point I would
suggest doing something so you have a known good ground, then proceed to
figure out what ELSE is wrong. 

> Would adding a #31 wire eliminate the need for the gauge housing 
> ground as the dash (thus making it unnecessary for me to figure out 
> how to finally seat this darn thing?).

Yes.

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

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