Hi there. I don't think you should worry. Since the 55s is the basic model, it doesn't have a temp gauge on the clock. However it does have an overheat warning light on the upleft corner of your fuel meter, which will flash when the temp sensor detects an overheat. Your fan kicking in is a good sign that the temp sensor's working properly. But do check if the coolant is ok or if there's any leak just in case! Hope this helps!