The fuel and temp gauges use the output of the 10 volt regulator, also
called the dash voltage stabilizer. That is what powers them, not the
direct voltage from the alternator. This 10 volt regulator is used
exactly because without it the gauges would have different readings when
the vehicle voltage differed, such as when headlights and heater fan
were on. The stabilizer/regulator steps down the varying 12-14 volts to
a lower but constant 10 volts just for the gauges.

Mark

Kim Brennan wrote:
> This can vary, vanagon to vanagon. ..............
> Also, since the fuel guage is driven by voltage, if you have low
> voltage from your alternator (or are running on battery), the gauge
> will read lower. Conversely with a subaru alternator putting out 14
> volts, it will read higher (and hence mislead you as to how much gas
> you really have remaining.)
>
> Data on my tristar, however was with stock VW engine.
>
> On Jan 27, 2009, at 9:06 PM, Mike Collum wrote:
>
>> Mike S wrote:
>>> Red _is_ reserve. It's just that to the Germans, empty is empty, so
>>> the
>>> reserve is the last bit before the tank is empty. Consider the red a
>>> warning that it's time to buy gas.
>>
>>
>> Well, FWIW, the red or "Reserve" area on a Vanagon fuel gauge is 1/4
>> tank ... or just under 4 gallons left in the tank.  I wouldn't count
>> on
>> it being more than 3 gallons, though.
>>
>> Mike
>
>