On my 91 1.8 the temperature sender is part of the temperature controlled switch which turns the fan clutch on and off. 2 of the pins turn the fan on when shorted and the one thats on its own is the temp sender.

Mine is a 3 pin unit and I think earlier ones have just the one or two pins. Anyway the temp gauge shows min when its not connected to anything and max when shorted to earth.
On my car the sensors are at the top of the engine block at the very front and to the right if looking at the front of the car. There are 3 or 4 holes which each may hold a sensor or be empty (with a bolt to fill them) depending on model.