poultergeist

Hi all,wondering if you can help. Recently got back in a Ford in the shape of a SportKa. I bought it with the Engine management light on but it drove fine so wasn't TOO worried,got it Home and got a mate to plug it in and turned out to be coolant temp sensor. Today the car overheated and pretty sure fan didn't kick in,is this all controlled by the cts or am I looking at bigger problems??

Any help would be greatly appreciated :-(