When I have my heater on makes a terrible grinding noise

What is your question?

One day I was driving with my heater on in my 2003 kia sorento all of a sudden there was a terrible grinding/screeching sound then it stopped. A few more miles it did it again so I turned my heater off and it hasn't done it since. (Haven't been driving with my hearter on and its gettimg cold ) what could it be?