1995 Buick Century Limited - 3.1L V6

My Buick's cooling system works but seems to be slow in activating the fan when I'm in traffic, stop etc. The temperature will seem to go up to almost the red, then the fan will kick in, cooling it back to normal. While working, it seems to be delayed. I receive no lights on the console. What sensor controls the fan and where is it located, I believe that while not broken, it might be faulty? Would it be the Coolant Temperature Sending Unit perhaps? Thanks.