Anyone got a SPA brake bias gauge fitted?

[tvrolet]

...and got a wiring diagram? Trying to get the one that came with the car working but it keeps flashing up a fault. Could well be a dodgy sensor but the wiring looks pretty butchered, so anyone know a) what the pin-outs at the back of the gauge are, and b) what the connections are on the sensors themselves? Also, do you have to callibrate these things as when I've permutated the wires on the sensor to get some sort of reading I'm never getting a zero pressure?

Thanks