Thermostat issues ep70

[Fathead]

Hi all 

I hope someone can help out here . have a ep70 that its temp gauge is going into hot as soon as its ran for 2mins .. No oil in water no water in oil , no air in system . new thermostat , new sensor . new water pump..

So its wiring issue   would someone agree ??? 

I ran a wire from sender direct and gauge goes straight into red without engine running .. 

Would someone have a wiring diagram or advise please ?? 

Its a 1lt boxey ep70 1985