[T2] Gas gage weirdness

[Al Brase]

Long term storage seems to take a toll on the senders, for sure. The older
ones are quite delicate inside.

On Thu, Feb 21, 2019 at 11:16 PM c.dreike <c.dreike at verizon.net> wrote:

> Thanks for the tips guys. Yes the "vibrator" assembly is a feature on
> bay window buses, however only sometime after 1972. The function of the
> gizmo is to stabilize the voltage for a consistently accurate reading.
> The device is actually a voltage regulator. If you look on The Samba you
> will find some descriptions of what it is and what it does. This does
> however give me an additional idea for my operational amplifier design.
> I'll add a voltage regulator for more stable operation.
>
> I'll whip one of these together over the next few days and let everyone
> know how it works out. In the mean time maybe someone will pop up with
> another idea of what I might be doing wrong. I mean, VW built these
> things for years and they worked just fine. I'll take a look in on my
> splitty and see what that's doing. That gas gauge is working fine.
>
> Cheers,
> Chris
> 71 Sunroof
> 64DD Kamper Kit
>
> On 2/21/2019 4:47 PM, c.dreike wrote:
> > Started testing my gas gage and sender. The sender worked when I
> > installed it. Currently the tank is very low and the sender reads
> > about 80 ohms. According to The Samba this is about correct. The
> > senders run from about 3-5 ohms at full to about 70-80 ohms at empty.
> >
> > When connected, both of the gauges I have read full and a little past.
> > The battery voltage is about 11.98. The voltage across the gauges are
> > 6.57 on the original gauge and 7.98 on the reproduction gauge.
> >
> > On the test bench connected to a bench supply, the original gauge
> > reads full at about 6.5V and the reproduction gauge reads full at
> > about 7.2V. As I reduce the voltage to the gauge, the reading goes
> > down. At 0 volts the gauges read empty.
> >
> > Per the test specs in Bentley, the gauges should read full at about
> > 12V, battery voltage. Both my gauges peg when attached to full battery
> > voltage.
> >
> > I have double checked the wiring against the schematics and all looks
> > correct. The circuit looks simple enough. +12V on one side of the
> > gauge. The other side of the gauge connects to the sender (5-80 ohms)
> > and the other side of the sender connects to ground.
> >
> > I'm an electrical engineer with lots of experience with simple stuff
> > like this and this stuff makes no sense to me. I must be missing
> > something. (Kinda like mistaking the wire stripe colors on the turn
> > signal)
> > Anyone have ideas on what I should be looking for or doing
> > differently? I'm stumped. I'm about to build an inverting operational
> > amplifier circuit that would drive the gauge so that it would see 0
> > volts at empty and about 7V at full.
> >
> > TIA
> > Chris
> > 71 Sunroof
> > 64DD Kamper Kit
> > _______________________________________________
> > type2 mailing list
> > type2 at type2.com
> > https://www.type2.com/lists/type2/listinfo
>
> _______________________________________________
> type2 mailing list
> type2 at type2.com
> https://www.type2.com/lists/type2/listinfo