401 Fuel Gauge or Sender Problem.

[Geoff Kingston]

One of my least favourite things on cars is their electrics, Mike and I had a frustrating morning yesterday trying to get the fuel gauge to move off empty having reconnected the loom, the job was not helped by a faulty Draper test lamp/probe which having been led astray by the thing myself today is now in the bin.
Using a volt meter I have established without doubt that we had the correct wire and the reading I am getting on the feed going into the gauge is the same as the reading on the connection to the sender, around 12.4 volts , when the feed was connected to the sender nothing happened Mike then ran an earth from the sender unit to the chassis still nothing not even a flicker.
Today with the test meter I observed that if the earth wire is connected to one of the screws on the case the reading at the connection to the power feed into the sender drops to just under 3 volts, disconnect the earth and it goes back up to 12.4v, also with the earth lead off I get a reading of 12.4v anywhere on the case of the sender unit, is this normal or is it indicating there is an internal short in the sender unit.
Geoff.