I've literally replaced every component in order to get the fuel gauge in my '70 Bug to work and no soap. I've even swapped parts between my '68 and the '70 and still no good. I connected a test light between the sender wire and grounded the test light on the speedo and got a very dim light, whereas the same test on my '68 (with working gauge) had a nice healthy beam from the test light. Mind you, I've run a new German sender, vibrator/resistor unit and gauge as well, only to no avail.
Anything I might be missing would be greatly appreciated!