'90 90 20V Gas Gauge

[Peter Tracy <pgt@ekbos.com>]

My gas gauge is not working. Assuming it must be the sending unit, I
measured the resistance as follows:
Tank Full: 44 ohms
1/3-1/2 Full: 75 ohms

The Bentley manual seems to imply that at reserve you would have 149
ohms, so my measurements might make sense.

I also measured the voltage at the two leads to the tank sending unit. I
only got about 65 mV. Does anyone know what voltage should be there.
Bentley doesn't seem to say-you are supposed to troubleshoot this stuff
with special VW tools.

TIA
Peter