Fuel Gauge Voltage Question

Hello
I am having problems with my fuel gauge not reading more than 1/4 full when the tank is full of diesel. I have tested the gauge on a battery and the needle is going from empty to full. I have tested the live feed to the gauge which is reading 12V no problems here. I then disconnected the lead going to the sender and connected the meter to the terminal on the gauge but it only reads around 4V. When I disconect the earth connection on the gauge the terminal going to the sender unit reads 12V.

Anyone got any ideas before I splash the cash and buy a new sender and gauge.

Thanks
Jamie

Gauge sounds OK

Take the sender out the tank - quick and easy and test.

Will eliminate if sender or wiring - but if you want a short dut, pull wire from gauge, bridge directly to battery and see if gauge reads fall

Thanks for the reply.
I did pull the sender from the tank and moved it manually but the same problem only reading 1/4 full.
I will try and earth the gauge directly to the battery tommorrow.
Should I be getting 12v at the tank ????
The sender unit has three terminals on it all in a row. I am would like to check that the wires are on correctly.
I am under the impression that there is one from the gauge, one that goes to the low level indication and one for earth.
Anyone have an idea which wire goes where.

Thanks
Jamie

just earth each wire one at a time on any piece of clean metal with ignition on and watch guage and light

Dont have a problem with identifing what each wire is for but its with the terminals on the sender as each one is the same male spade connection all in a row.
Thank
Jamie

but it will tell you if fault is at sender or not ,you can trace wire if you lift sender out

Thanks for the replys
Will have a look tommorrow