[T3] Strange Fuel Gauge Behavior

[Jim Adney]

On 1 Jun 2017 at 21:53, Doug Brashear wrote:

> When I first turn on the car, the gauge needle instantly jumps up to
> the appropriate level based on the fuel in the tank. The reading does
> seem to be accurate. But when the tank is full, the instant travel
> sometimes get the needle stuck at "full". My other VW fuel gauges send
> the needle to the appropriate level slowly...not the case here. 

The instant response sounds normal. When I've had gauges that seemed 
to get stuck on F, the stickyness was in the dash unit. A good tap 
would release them. If it's in the sender, it can be cleaned, gently, 
with care. I'd expect regular use to clean it up, unless the problem 
is rust on the rod that the sender float rides on.

I can clean it up, if it needs any special care.

> Then, when the car is fully off, and I turn on the parking lights and
> the 4-way flashers, the needle jumps back and forth with the blinking
> of the flashers. 

That seems to happen when the dash unit isn't getting a good ground. 
I've never understood why this would be the case, because this seems 
to happen even in '69-on cars where the dash gauge got a dedicated 
ground wire.

To test this, try moving the dash unit around while it's doing this. 
You'll probably find that you can make the problem go away in some 
positions. The problem seems to be caused by the padded dash 
shrinking with age, which reduces the tension on the mounting clips, 
but it can also be caused by the spring clips being forced outside 
the little humps that they should ride up against. You'll probably 
have to take the clock out (because that's the easy one) to see what 
I'm talking about. Just feel the backside of the metal dash where the 
spring clips seat.

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