My 2006 Ford Fiesta 1.25 petrol has developed a coolant leak. When it initially happened the warning sign came up on the display and the temperature gauge was in the red. I stopped the car immediately and let it cool down before driving it again after topping up with water.

I traced the leak to the thermostat housing and replaced it. Although the leak has stopped I’ve noticed the fan doesn't turn on which is probably why the thermostat housing got the leak. I have tested the fan with a 12v direct feed and it works ok. I’ve also checked the fuses and wiring and can’t see any visible problems. Should I replace the coolant sensor or maybe a relay?