my radiator fan does not work on my renault twingo 210?

On my renault twingo 2010 1.2 petrol engine the radiator fan doew not switch in after a 30 mile jounrney nor does it turn on when stopped at the end of the journey. I hav ejust replaced the water punp timing belt and coolant water for some maintenance. But noticed that the fan behind the radiator does not come on yet the engine is hot and if the airco is on the fan turns. what is the issue, the thermostat? but cannot check the engine water temperature no gauge.