260Z temp guage switch at thermostat housing

[Lynton]

I have put in a new 260z heat temp switch at the thermostat housing and used original wire and connector this all seems ok.

 

I have also put in a new 280zx temp guage switch at the thermostat housing using a 280zx wiring loom but I am not getting a temp guage reading?

 

Should one of the two wires from the temp guage switch go to an earth?

The new switch is different (2 pronged) from the original switch the 260z had...thanks Lynton