My E270 has been suffering from low temperature 50-60 degrees. After reading several threads it was clear that I should replace the thermostat. I now have the thermostat and am going round a friends to replace it this evening. However when I stopped at a shop to pick up the oil filter removal tool while checking I have the correct one I noticed that the fan was turning while the engine was running and the temperature was only about 70 degrees. Does this mean that I really only needed a temp sensor or would you expect this ?