>
> the real solution to all of this is to either find a dealer that has the
> vw special tool and actually knows how to use it.  or to figure out how
> the tool works ie what resistance equals what position on the gauge, and
> or what resistance equal what temperature.

I did a little archive dredging a few months back on the subject of the
VW1301 tool and came up with the following:

VW1301 is apparently a variable resistor device on a 12V input. There are a
few mentions of it in the archives. Ken Lewis did a test with a decade
resistance box and came up with some numbers, but I think he had the "fuel
full" and "fuel empty" numbers reversed. The markings on the VW tool are a
German engineering mystery. The proportion seems to be 5:3 in terms of
"VW1301 number" : "resistance in ohms". Ken himself even mentioned the
3/5ths thing at the time.

What it comes down to is: ("tool" means VW1301 tester dial setting)

tool = 50 ----- 35ohms (tank reads full, temp reads hot)
tool = 320 ---- 210ohms (tank reads empty)
tool = 510 ---- 340ohms (temp gauge reads cold)

--
John Bange
'90 Vanagon - "Geldsauger"