Help!

Can anyone help me with my landrover defender 300tdi,i have changed the thermostat and coolant sensor but when i turn the igntion on (even when cold)it shoots straight into the red(this was happing before i change anything)?

What is the diffrents between the red,black and green sensor as i have replaced the sensor with a green one instead of a black one?

Thanks in advance.

whats the code on the old sensor and the new sensor

if you disconnect wire from sensor and switch on ign. what happens to the gauge then?(test procedure)

sounds like the wires might be the wrong way round. the different colours refer to different temperature ranges I think.

part listed for 300TD1 engine temperature senders, green sender AMR1425
black sender AMR3321