Wiring fuel and temp gauge

[paulmmc]

The last thing left for me to wire up on my 1987 RRC is the fuel and water temperature gauges, i just can't figure out which are the relavant wires to connect into the back of the dash console.
From looking at the Haynes manual wiring diagram it seems that they share a common 12v feed but are individually earthed through their respective sensors.
So a 12v supply is fed into the fuel gauge and the earth wire is what is connected to the fuel sender unit in the tank, and the earth wire from the water temperature gauge goes to the water temp sensor in the engine. Is this correct? And has anyone any tips on which wires i need to connect to which. At the moment both gauges show full all of the time, and i have found a white wire that when it is connected to a 12v supply both dials show full.
Thanks

[Range Rover Blues]

Yes that's right, the water temp just earths through the block and it's a negative temp copefecient resister ie itgets hot and the resistance falls.  The fuel sender has a feed and earth but is basically the same, though the guages might not be interchangeable. 

If both read MAX then you have a short somewhere.

When the fuel guage reads lesd than 1/4 you may also get the low fuel light, this is run by electricery on the back of the instruments.

[Rossko]

The last thing left for me to wire up on my 1987 RRC is the fuel and water temperature gauges, i just can't figure out which are the relavant wires to connect into the back of the dash console.
From looking at the Haynes manual wiring diagram it seems that they share a common 12v feed but are individually earthed through their respective sensors.

I think that's almost right, but the 12V isn't applied directly to the gauges but fed through a voltage regulator to drop it to 9v or so.   If I remember right, this regulator is on a little PCB module that also works the tacho and low-fuel light.

[paulmmc]

Is the PCB module part of the dash or should i run the 12v feed through a separate PCB module before it gets to the dash? If so what does the PCB look like as i have the complete loom from the original rangie but I am only the bits i need so i may have cut it out without realising it. Is it one of the many coloured relay type things?
Thanks

[Rossko]

It's stuck in the back of the tacho.  You can treat the whole instrument cluster with its flexy pcb as a "black box" and just wire up as Mr.Haynes says.