Fuel gage/sender problem - how to test?

[Kerrigan]

My fuel gauge stopped working after the car sat for a month with a full tank of fuel.
I need to test to find out if the tank sending unit is bad or the gauge itself.
I can't make heads or tails out of the testing procedure offered in "that" UK printed manual.
Does someone know how I can test the tank unit easily?
Thank you!
Kerrigan

[zbane]

Potentially stupid questions here:
Have you checked that all of your electrical connections are clean and solid, from the sender to the instrument cluster?
How clean are the float contact points on the sender itself?

[Nissanman]

Refer to the thumbnail attached:
The gauge terminal of the tank transmitter can be temporarily connected to earth and that should force the gauge to read maximum scale, if everything else is working OK.
As mentioned, there are a fuseable link and a fuse to be checked in the Fuel Gauge circuit.
There is also a Voltage Regulator, shown at the LHS of the gauge, which controls the voltage applied to the gauge.
These have been known to misbehave and cause erratic readings usually on the Fuel and Temperature gauges.
Cleaning the contacts on the VR and all points in the diagram may remedy the problem.

[Curtis240Z]

An emtpy tank sender would read 90 ohms, a full tank 10 ohms. Nissanman is correct in diagnosing the wiring system, just ground the wire and it should read full scale.